It really depends on the puppy. There matabolisims are all different.
A puppy is not going to be finished growing until after it's a year old anyway, so don't worry about feeding too much.
If your vet is satisified with the growth of your pup, don't worry about it.
If your afraid your not feeding enough, give him/her a little more and see if he/she eats it. If so, continue giving a little more food until it starts leaving some food uneaten.
I free feed mine, so they always have food available.