
I would just go by how he looks. You want to be able to feel a light covering over the ribs and then tucked in at the waist when you look at him from directly above (although I do think an extra bit of puppy fat at his age is ok

).
My Dobe has always cleared his bowl in one go from day 1 (he's nearly 4 now) and would eat as much as I gave him I think, but his weight is perfect as it is. It's great to have a healthy eater. It doesn't necessarily mean that he needs more (unless he looks on the thin side obviously!) just that he enjoys his food

What is the weight range (of the dog) given for the 40-160g of food a day?