You can use any characters in combination with the starting number.
Just make sure there is a digit present. See examples below.

The default mode is "first group of digits".
If you have more than 1 group of digits (e.g. "S03E0"), try out the other modes.

Examples:

Starting number Result Enabled options/Mode
04 04, 5, 6 ..... Default
08 08, 09, 10 ..... Leading zeros
2021-%23%-08 2021-23-08, 2021-24-08, 2021-25-08 ..... %(number)% mode
4) 4), 5), 6) ..... Default
[4] [4], [5], [6] ..... Default
S01E04 S01E04, S01E05, S01E06.... Last digits mode
S01E04 S01E04, S02E04, S03E04.... First digits mode