Saxon 9 XSLT Transformation results in NaN

[jcsntoll]

I want to transform this xml file:\[code\] <?xml version="1.0" encoding="utf-8"?><KNX xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" CreatedBy="ETS4" ToolVersion="ETS 4.1.2 (Build 3013)" xmlns="http://knx.org/xml/project/11"> <Project Id="P-065C"> <Installations> <Installation InstallationId="0" Name="" BCUKey="4294967295" DefaultLine="P-065C-0_L-2" IPRoutingMulticastAddress="224.0.23.12" SplitType="None" CompletionStatus="Undefined"> <Topology> <Area Id="P-065C-0_A-0" Name="Backbone Bereich" Address="0" CompletionStatus="Undefined"> <Line Id="P-065C-0_L-0" Name="Bereichslinie" Address="0" MediumTypeRefId="MT-5" DomainAddress="0" DomainAddressIsChecked="0" CompletionStatus="Undefined" IPRoutingMulticastAddress="224.0.23.12" MulticastTTL="16" /> </Area> <Area Id="P-065C-0_A-1" Name="Neuer Bereich" Address="1" CompletionStatus="Undefined"> <Line Id="P-065C-0_L-1" Name="Hauptlinie" Address="0" MediumTypeRefId="MT-5" DomainAddress="0" DomainAddressIsChecked="0" CompletionStatus="Undefined" IPRoutingMulticastAddress="224.0.23.12" MulticastTTL="16" /> <Line Id="P-065C-0_L-2" Name="Neue Linie" Address="1" MediumTypeRefId="MT-0" DomainAddress="0" DomainAddressIsChecked="0" CompletionStatus="Undefined" IPRoutingMulticastAddress="224.0.23.12" MulticastTTL="16"> <DeviceInstance Id="P-065C-0_DI-1" ProductRefId="M-0002_H-2CDG.20110.20085.20R0011-1_P-2CDG.20110.20085.20R0011" Hardware2ProgramRefId="M-0002_H-2CDG.20110.20085.20R0011-1_HP" CompletionStatus="Undefined" IndividualAddressLoaded="0" ApplicationProgramLoaded="0" ParametersLoaded="0" CommunicationPartLoaded="0" MediumConfigLoaded="0" IsCommunicationObjectVisibilityCalculated="1" Broken="0" /> <DeviceInstance Id="P-065C-0_DI-2" ProductRefId="M-0002_H-2CDG110061R0011-1_P-2CDG.20110.20061.20R0011" Hardware2ProgramRefId="M-0002_H-2CDG110061R0011-1_HP-A035-10-377F" Address="0" CompletionStatus="Undefined" IndividualAddressLoaded="0" ApplicationProgramLoaded="0" ParametersLoaded="0" CommunicationPartLoaded="0" MediumConfigLoaded="0" IsCommunicationObjectVisibilityCalculated="1" Broken="0" /> <DeviceInstance Id="P-065C-0_DI-3" ProductRefId="M-0008_H-8.20.2F.2F.2018500-1-O0001_P-185.2000" Hardware2ProgramRefId="M-0008_H-8.20.2F.2F.2018500-1-O0001_HP-1058-01-D423-O0001" Address="1" LastModified="2012-09-07T14:20:33" CompletionStatus="Undefined" IndividualAddressLoaded="0" ApplicationProgramLoaded="0" ParametersLoaded="0" CommunicationPartLoaded="0" MediumConfigLoaded="0" IsCommunicationObjectVisibilityCalculated="1" Broken="0"> <ComObjectInstanceRefs> <ComObjectInstanceRef RefId="M-0008_A-1058-01-D423-O0001_O-0_R-5" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-1" /> </Connectors> </ComObjectInstanceRef> <ComObjectInstanceRef RefId="M-0008_A-1058-01-D423-O0001_O-1_R-11" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-1" /> </Connectors> </ComObjectInstanceRef> <ComObjectInstanceRef RefId="M-0008_A-1058-01-D423-O0001_O-2_R-23" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-2" /> </Connectors> </ComObjectInstanceRef> <ComObjectInstanceRef RefId="M-0008_A-1058-01-D423-O0001_O-3_R-26" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-2" /> </Connectors> </ComObjectInstanceRef> </ComObjectInstanceRefs> </DeviceInstance> <DeviceInstance Id="P-065C-0_DI-6" ProductRefId="M-0048_H-1319201-2_P-1319201" Hardware2ProgramRefId="M-0048_H-1319201-2_HP-131C-12-4C9E" Address="2" LastModified="2012-09-07T12:16:26" CompletionStatus="Undefined" IndividualAddressLoaded="0" ApplicationProgramLoaded="0" ParametersLoaded="0" CommunicationPartLoaded="0" MediumConfigLoaded="0" IsCommunicationObjectVisibilityCalculated="1" Broken="0"> <ComObjectInstanceRefs> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-12_R-209" IsActive="1" /> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-13_R-13" IsActive="1" /> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-14_R-14" IsActive="1" /> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-15_R-15" IsActive="1" /> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-16_R-63" IsActive="1" /> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-17_R-17" IsActive="1" /> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-4_R-68" IsActive="1" /> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-40_R-215" IsActive="1" /> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-1_R-2" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-3" /> </Connectors> </ComObjectInstanceRef> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-0_R-1" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-3" /> </Connectors> </ComObjectInstanceRef> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-7_R-8" IsActive="1" /> <ComObjectInstanceRef RefId="M-0048_A-131C-12-4C9E_O-8_R-122" IsActive="1" /> </ComObjectInstanceRefs> </DeviceInstance> <DeviceInstance Id="P-065C-0_DI-5" ProductRefId="M-0008_H-8.20.2F.2F.20570.2000-1_P-570.2000" Hardware2ProgramRefId="M-0008_H-8.20.2F.2F.20570.2000-1_HP" Address="3" CompletionStatus="Undefined" IndividualAddressLoaded="0" ApplicationProgramLoaded="0" ParametersLoaded="0" CommunicationPartLoaded="0" MediumConfigLoaded="0" IsCommunicationObjectVisibilityCalculated="1" Broken="0" /> <DeviceInstance Id="P-065C-0_DI-7" ProductRefId="M-0007_H-2CDG.20110.20079.20R0011-1-O0002_P-6197.2F22" Hardware2ProgramRefId="M-0007_H-2CDG.20110.20079.20R0011-1-O0002_HP-A043-12-5DB8-O0002" Address="4" LastModified="2012-09-07T14:20:45" CompletionStatus="Undefined" IndividualAddressLoaded="0" ApplicationProgramLoaded="0" ParametersLoaded="0" CommunicationPartLoaded="0" MediumConfigLoaded="0" IsCommunicationObjectVisibilityCalculated="1" Broken="0"> <ComObjectInstanceRefs> <ComObjectInstanceRef RefId="M-0007_A-A043-12-5DB8-O0002_O-10_R-2438" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-1" /> </Connectors> </ComObjectInstanceRef> <ComObjectInstanceRef RefId="M-0007_A-A043-12-5DB8-O0002_O-12_R-2319" IsActive="1" /> <ComObjectInstanceRef RefId="M-0007_A-A043-12-5DB8-O0002_O-13_R-2443" IsActive="1" /> <ComObjectInstanceRef RefId="M-0007_A-A043-12-5DB8-O0002_O-34_R-2433" IsActive="1" /> <ComObjectInstanceRef RefId="M-0007_A-A043-12-5DB8-O0002_O-35_R-2440" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-2" /> </Connectors> </ComObjectInstanceRef> <ComObjectInstanceRef RefId="M-0007_A-A043-12-5DB8-O0002_O-38_R-2450" IsActive="1" /> <ComObjectInstanceRef RefId="M-0007_A-A043-12-5DB8-O0002_O-59_R-2432" IsActive="1" /> <ComObjectInstanceRef RefId="M-0007_A-A043-12-5DB8-O0002_O-37_R-2316" DatapointType="DPST-3-7" IsActive="1" /> </ComObjectInstanceRefs> </DeviceInstance> <DeviceInstance Id="P-065C-0_DI-8" ProductRefId="M-0008_H-8.20.2F.2F.20880.20xx-1_P-880.20xx" Hardware2ProgramRefId="M-0008_H-8.20.2F.2F.20880.20xx-1_HP-A003-01-737E" Address="5" LastModified="2012-09-07T12:16:43" CompletionStatus="Undefined" IndividualAddressLoaded="0" ApplicationProgramLoaded="0" ParametersLoaded="0" CommunicationPartLoaded="0" MediumConfigLoaded="0" IsCommunicationObjectVisibilityCalculated="1" Broken="0"> <ComObjectInstanceRefs> <ComObjectInstanceRef RefId="M-0008_A-A003-01-737E_O-0_R-0" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-4" /> </Connectors> </ComObjectInstanceRef> <ComObjectInstanceRef RefId="M-0008_A-A003-01-737E_O-1_R-1" IsActive="1" /> <ComObjectInstanceRef RefId="M-0008_A-A003-01-737E_O-2_R-2" IsActive="1"> <Connectors> <Send GroupAddressRefId="P-065C-0_GA-4" /> </Connectors> </ComObjectInstanceRef> </ComObjectInstanceRefs> </DeviceInstance> </Line> </Area> </Topology> <Buildings> <BuildingPart Id="P-065C-0_BP-0" Name="Hauptgeb?ude" Type="Building" CompletionStatus="Undefined"> <BuildingPart Id="P-065C-0_BP-1" Name="Vordergeb?ude" Type="BuildingPart" CompletionStatus="Undefined" /> <BuildingPart Id="P-065C-0_BP-2" Name="R