If I'm reading the .XML file correctly, the Pnx file is for preprogrammed phone number lookup:
</File></DataType><DataType><Name>PreProgrammedPhoneNumberLookup</Name><File><Specification><Identifier>PNX</Identifier></Specification><Location><Path>Garmin/Pnx/</Path><FileExtension>pnx</FileExtension></Location><TransferDirection>InputOutput</TransferDirection></File></DataType><UpdateFile><PartNumber>006-F0057-
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