@HellHarpi
No worries! I'm here to help and answer questions!
You actually don't have to do anything with the digits column. There is a formula in cell D3 that calculates it for you once you put your Wolfs ID into column C.
So for example: if your Wolfs ID is 1234, once you enter that, it will automatically put a 4 in column D.
As a fix check to see if cell D3 contains this formula:
=ARRAYFORMULA(IF(C3:C1001="", "", LEN(C3:C1001)))
If it doesn't, copy/paste the formula back into the cell and it should fix itself.
If that doesn't work, let me know if there any error code or #REF that shows up in the column.