To Ludia, I hope for your sake you do this right with the boost return or your support staff are going to have a very very bad week or three.
Everyone go through your creatures and write down and calculate how many boosts were applied so you know how many you should get back. I have quite a few unused on top of what what I have applied. If you don’t have excel, you can use google sheets. Any more you buy or earn between now and the update, you can just add in to the unused.
Example of my 2 accounts: