2.1.214 Part 4 Section 2.6.9, paperSrc (Paper Source Information)
a. The standard states that the first and other attributes can be any integer.
Word restricts these values to the range of an unsigned short.
b. The standard simply states that this element's attributes specify "...a printer-specific code that uniquely identifies a specific printer tray..."
Word passes this value to the Windows DEVMODE printing API [DEVMODE] where the value may have a standard meaning to Windows or an installed printer.