Let me see if I can explain this more clearly.
Any GC that you buy from one of the online discounters has the potential to be used by the original owner if they held onto the GC number and the pin code (or what Target calls the access code).
Even if you purchased a physical GC and have it in your hands, the owner can still make online purchases with that card if they have the GC # and access code.
For that reason, you want to "move" the funds on those cards to a GC of your own. Adding the GC from Raise (or cardcash, or cardpool, etc.) to your Target .com account is not going to protect you, since the original owner may still have all the info he needs to use those funds himself. You need to transfer the funds to another GC to protect the money. You do this by combining those GCs on a "safe" GC that only you have owned.
To combine Target GCs, you need the Target app for your mobile device. It will link you to the mobile target gift card website sign in page when you tap the my GiftCards link. You will want to add your "safe" Target GC first. Then your new GCs can be saved to the account and combined on the safe GC.