I dare say it may have been suggested...
In the renamer, $number: needs a starting position as 1 isn't always wanted.
What may work is to have on the replacement box end menu a second one, $number,start,step,minlen: (min length pads with 0s) which it inserts and you replace the three words with your values, e.g. to $number,10,2,3: which would start at 10, proceed in steps of 2, padding numbers with 0 to make a min length of 3, with omitted/non-numeric parameters taken as 1.
Thanks!
David