I am feeding my 12 week old puppy Bil Jac puppy. He has been receiving 3 cups a day. My vet said to feed him according to the bag. He weighed 31lbs at 11 weeks. and the bag suggests 20-30=3cups, 30-40=4cups and so on, I do not want to overfeed him is 4 cups to much for him and should I go by the bag suggestions?