[Answered] BCID #
Am I able to change the number to the number that’s on the bookplates?
I would leave the books you already registered with the numbers you've already given them and use your new pre-numbered labels on other books when they arrive. (And don't forget, you make a journal entry to register books with a pre-num, so don't go to Register Books, as that will give you yet another new number.)
Have fun getting to know all the ins and outs of BookCrossing! It will get easier and more fun as you go!