On watermark feature (option Alphabet:Roman), Numbers (1, 2,3 ... ) are not correctly written in the pdf output

[YASSINETAOUIL]

When I try to add watermark without any digit number. it is working fine.
But when i try to add digit number or ":" or "-" or "," the output is different random characters.

I don't know if this is bug in Roman alphabet or should be a request for new alphabet (like english).

Input:

Output in PDF:

[sbplat]

The other fonts don't have this issue so it might be something with the font.