Spoiler Slayer

As was mentioned in the comments, I did catch the continued numbering of the shirts. Dawn wore both a 2 and a 55. Now that there is a number that can't be related to a month, or bankruptcy, or even a letter (55), I almost feel as if Joss is just having fun with us. I haven't seen anyone else do it yet, but the numbers could coincide with episodes (much like the 730 did with days until Episode 100).

2 - The Harvest
7 - Angel
11 - Out of Mind, Out of Sight
13 - When She Was Bad
55 - Graduation Day

But that doesn't really make any sense either.