Xerox 4450 - Manual (Page 86)

SUPPORT TOOLS AND MEASUREMENTS
Side 1 Side 1 of the ruler is typically used for measuring impact-printed
computer output reports in which the spacing is 10 cpi (scale 1)
and either 6 lpi (scale 2) or 8 lpi (scale 3).
Side 2 Side 2 should be used for measuring laser printing systems
output.
Default spacing The default spacings on the system are 13.6 cpi (scale 5) and 8.1
lpi (scale 6); they were chosen for optimal readability for the
standard computer format of 132 columns by 66 lines.
Reference Refer to the “Standard print formats” appendix for a complete list
of standard formats and spacings.
F-2 XEROX 4050/4090/4450/4650 LPS FORMS CREATION GUIDE