Epson EPL-N3000 Reference Manual page 415

Font size
The following codes are inserted automatically and need not be
input by hand:
Left/Right quiet zone
Start/Stop character
Check digit
The numeral "0" (added to the beginning of character strings
as needed)
402
Working with Fonts
When OCR-B is not used: 26 pt or more (up
to 96 pt in Windows XP/2000/NT).
Recommended sizes are 26 pt, 52 pt, 78 pt,
and 104 pt.
When OCR-B is used: 36 pt or more (up to 96
pt in Windows XP/2000/NT).
Recommended sizes are 36 pt, 72 pt, 108 pt,
and 144 pt.