Leading Zeros

I use the Advanced Renamer to rename files in student directories often containing many thousands of pictures and files. I have a small problem in that I like to have consecutive filenames in the form of numbers say, 1 - 2000. This becomes horribly taxing though because my renamer has started to include a mass of leading zeros in the new filenames. As you can appreciate having file 1.doc suddenly become file 00001.doc is a nuisance and is very space consuming.
Can anyone tell me how to get the program to stop inserting the leading zeros into the new filename ?

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