ggzh, thanks for the clarification! I do actually keep a list of the items donated with the blank receipt.

I guess this is again somewhat of a honor system -- if you have, for instance, three skirts that you want to donate, you can donate one each time and get three receipts and then claim $250*3 (and you have receipts to prove that you donated three times), which is actually cheating but nobody would be able to tell.