Numbering playlist tracks.

iTunes won't list my tracks chronologically once they get past 9. I have a lecture series that has 30 tracks in it and when I number them from 1-30 as soon as iTunes sees another 1, like at the beginning of all the numbers from 10-19, it puts them after the number 1, and then moves onto the number 2. It's a real drag and other than alphabetizing the first 9 numbers I'm at a loss of what to do. Is there somewhere in preferences I can have it recognize two-digit numbers properly? Thanks.

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