Well, not sure what to say. They are unique, (e.g. 0011, 0021, 0031, etc)., and would be even if the "1" weren't appended (001, 002, 003). It's just as if PM wants to add that 1 just in case later the user might want to slip a few in between. But there's no getting around it, as I've tried.
Have you tried the function in PM to see if you get the same thing?