User mapping greyed out

Having an issue where I can’t link a guest author to a real author account, the fields are greyed out under user mapping. Is this because the author already exists with the same slug and it automatically knows to assign it to them?

Right now when i search for the author’s name in a post 2 show up. Not sure which is the guest author and the real author.

IN this case, should I just delete the gust author and assign the posts over to the real author when it asks to do so instead of linking?

https://wordpress.org/plugins/co-authors-plus/