The CREDINTIALS.CFG file

As far as Google Play is concerned, the archive is a phone/tablet. As such, it must contain the same credentials, a real device would provide.

Username

The username of a Google Account (this takes the form of an email address). You can use your regular Google Account, but you shouldn't.

Password

The password of the Google Account. Keep in mind that it will be stored in the archive and everyone with access to that directory can recover it (that is one of the reasons not to use your regular Google Account).

GSF ID

A (pseudo) unique hex string. Every phone randomly creates one when factory reset. You don't need to supply this one. If you don't, Raccoon will simply create a fresh one.

It is strongly recommended not to use your regular Google Account/Android ID. If you do, make sure you are not mix and match. Regular account and fresh ID is possible, but you'll find a new phone registered to your account afterwards.