Yes, during proofing we will notify you of any size changes and update your total price accordingly. This makes your ordering easier if you don't know your exact size. You can enter an approximate size during checkout and then we'll update your size and price during proofing to reflect the actual size of your stickers.
For example, you might order a 76 mm x 76 mm die cut but the actual size of your sticker is 71 mm x 76 mm. Since the actual size is slightly smaller than the ordered size we'd reduce your price automatically to charge for the cost of a 71 mm x 76 mm.