How to say hashcat to start 8 numeric and continue till 12 digits?

I have already read several scripts and this forum, in specific, but i couldn't find my specific question straight:

How to burteforce a WPA2 starting 8 digits, numerics only, and continue till 12 digits?

I thank in advance.
..

For an example, here is a thread I visited: https://hashcat.net/forum/thread-4095.html and https://hashcat.net/forum/thread-9634.html