[Lady Fitzgerald]

I'm trying to make a custom column for numbers assigned to books (not series numbers). The numbers can range from 1-999. It appears "Integers" is the column type I need to use but I have no clue what to put in "Format for numbers". I need the column to be right aligned and would prefer not to have to use leading zeros for proper sorting.

I want the column to look like something like this before sorting (only right justified; the forum software wouldn't let me put in leading spaces to emulate right justification):
9
13
10
1
109
243

And something this after sorting (again, only right justified):

1
9
10
13
109
243

I tried to figure out the Python documentation but I might as well had been reading Sanskrit. Can anyone tell me what I need to put in the "Format for numbers" field?