Here are the Crystal RDC (print engine) values for PaperSource including 15. I don't know the meaning behind these but I hope this helps in some way:
crPRBinUpper - 1
crPRBinLower - 2
crPRBinMiddle - 3
crPRBinManual - 4
crPRBinEnvelope - 5
crPRBinEnvManual - 6
crPRBinAuto - 7
crPRBinTractor - 8
crPRBinSmallFmt - 9
crPRBinLargeFmt - 10
crPRBinLargeCapacity - 11
crPRBinCassette - 14
crPRBinFormSource - 15
PaperSource:
http://goo.gl/B2hyMW
On this page if you click on the left naivgation arrow in bottom left you can get values for PaperSize and PaperOrientation too.