Epson TM-P20 Technical Reference Manual page 87

Requirement for black mark printing
(1)
Preprintable area
(2)
The allowable relation between the reflecting rate in the black mark portion (1) and the non black mark portion
(2) must be as shown in the below:
Black mark portion (1):
Non black mark portion (2):
The reflecting rate means the value which is measured with a Macbeth density meter (PCMII) D filter.
15 or
21.25 more 21.25
16% or less
85% or more
30 to 300
3 to 5
Units: mm
Appendix
87