Amazfit Watch faces

Q1-I want to design numerical digits with transparent portions. Then how to add a new transparent portion to an existing digit like "_2". Where 2 is the existing digit and the underscore is an added transparent part of the digit.

Q2- What should be the resolution (pixels/inch) of a digit in BIP watch face?

I use Paint.net for editing watch faces.

I would appreciate solutions to the issues I mentioned above. Thanks in advance.
Regards.
Asadul Huq

1、DPI: 96

2、edit IN Paint.net OR superposition in WATCH FACE editer