Late on the reply but you do not have to log the purchase pieces you had prior to the license, but you will have to log selling them.
Do you have some other records of purchases? I don't know how much trouble it would be, if you were audited and had some not on the list.
What I did was log them anyway with original purchase date and just made a note that C&R not used in purchase.
Do you have a link for having to "log out" pieces that aren't in your book/that you had prior to the license?