Lexmark C910 Reference Manual page 219

setuniversalsize
changes the current settings for the Universal paper size. Each parameter on the
stack indicates:
Universal Width
Universal Height
Universal Feed Direction
short edge
long edge
Custom Universal Prompt String
Error: rangecheck, stackunderflow, typecheck
4-23
minimum to maximum width in points
minimum to maximum height in points
String must be 16 characters or less.
PostScript