Originally Posted by DiapDealer
I think it means... don't go trying to sync non-Amazon content when your Amazon archive has that content in it already.
Seriously, though... I'd test it on books that you don't
have Kindle versions of already. That way, it doesn't exist in your Amazon archive... and you won't potentially be mixing and matching different versions of the ebook file.
Ah Ha! Your brilliance knows no bounds. That makes a lot of sense. I'll try it out later. This could end up being a wiki page.