mask question

If I understand it correctly, mask "?d?d?d" will generate all 3 digit numbers from 000 - 999; But what if I just want to generate numbers from 200 - 399, i.e., the 1st digit is either 2 or 3?

I am thinking that the mask should be [23]?d?d, am I correct? If not, what's the right mask?

Thanks for your time!

please read and --help.

What you should investigate is what custom charsets do (--custom-charset1, --custom-charset2, --custom-charset3, --custom-charset4 or short form -1, -2, -3, -4).

This should work:
-1 23 ?1?d?d
thanks for your helpful advice. your solution is exactly what I wanted.