I would definitely see what size the "adult rats" were that he was eating. If she can't tell you then well, that's kind of not so great I would think personally as a buyer's point of view. Also you want to get a rat that's large enough to leave a lump in him but if she was feeding smaller than what he should be, that could be a problem too cuz he may not take the larger feeder right away.
Congrats and keep us posted
