Pentax 3 User Manual page 42

Form Length:
This command can be used to set the form length of a 'Custom'
size page. You may specify the vertical print area in text lines
as defined by the 'Text Line Spacing' setting, or in inches.
If using the 'Lines' method for setting "custom" form length, the
physical height of the page is determined by the vertical space
per line as determined by the 'Text Line Spacing' command.
The minimum value allowed is the number of lines that would
equal at least one inch of print because this is the minimum
length of paper that will feed properly through the printer.
For example, if your current 'Text Line Spacing' is set to 6 lines
per inch, you must specify at least '6' lines of form length. The
maximum setting is 127 lines. For 6 lines per inch, that will
provide a page of a little more than 21 inches in length.
If using the 'Inches' method for setting form length, the physical
height of the page is rounded down if needed to create an
even number of print lines as determined by the 'Text Line
Spacing' command. For example, if your 'Text Line Spacing'
is set to 6 lines per inch, and you specify 9.6 inches, the
application will determine that 57 lines could be printed in this
space, and change your inch value to (1/6 x 57) and the
display a form length of 9.5 inches.
If you switch modes from 'Lines' to 'Inches', the form length will
be recalculated in inches and displayed accordingly. If you
switch from 'Inches' to 'Lines', the form length will also be
recalculated and displayed as the number text lines that will
be printed as shown in the example below.
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