Datamax Prodigy Operator's Manual page 138

N: Identifies the 5 digit addendum code for UPC fonts. It is a
numeric-only bar code with a fixed length of 6 characters. Five
characters supplied by the host or application software, the sixth
digit checksum supplied by Printer. If the sixth digit is sent by
the host, the Printer will check that character against the
calculated checksum and will print the bar code as all zero if
they do not match. The normal ratios that the Printer can print
are 1:1, 2:2, 3:3, 4:4, 6:6, and 8:8. These ratios actually specify
size of elements since UPC type bar codes are element based and
not ratio based. It must be place after the UPC/EAN code
manually. This code should be placed 9 modulus away from
the end of preceding bar codes.
203 DPI Printer 152 DPI Printer
Page - D22 Appendix D