If an item is attached to the wrong bib, you can "relink" the item to the correct bib and keep all the statistics and normal historical data that you would lose if you were to simply delete the item and then add it to another record.
The instructions for "relinking" are in the google Drive at:
https://docs.google.com/document/d/199v6vmcl5s0k0rye6pptsF78Cav3RKrKebzuYA8qA5A/edit?usp=sharing