I think you are right to be concerned with this advice. If the dog put on that much weight in a week, that is a lot of growth.
Fromm should be good food.
Lots of vets think you are working with crappy food like Purina or Iams. And you WOULD have to feed a lot more of that food. Look at the calories of those and see how much they suggest for a puppy of your weight and age.
But the food you are feeding is probably calorie dense, and probably 3 cups of that = 5 cups of the other stuff, all in all.
Remember that a little thin is a whole lot better than overweight. Better for heart and joints.
Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.