#72 v2 insert '0' @ position auto-adds a '.' @ end - why?

[Si Dedman]

So i'm adding zeroes into files called:
jpg-1
jpg-9
jpg-10
jpg-99
jpg-100
etc

So i want to pad 1-9 with 2 zeroes and 10-99 with 1 zero. But doing so adds a period at the end, seemingly for no reason. Please can you try to replicate?

Thanks