I'm not an expert at all!!!! but...

I think it's individual to any dog, but ANY weight gain is good when their puppies. Just because a puppy's parents are one size and you
expect her to be a certain size doesn't mean that's what her actual size will be. It's one of their little surprises for us, since it seems like they're the only ones that know how big they'll get.
As a frame of reference when Zoë went to the vet at 8 weeks old she'd weighed 2 pounds even (with her breeder). When I first took Zoë to the vet at 11.5 weeks old, she weighed 2.5 pounds. Well at 16 weeks old she's barely over 3 pounds. The vet had originally "planned" or guesstimated that she'd gain a pound in a month. She gained 1/2 a pound in a month, which was still enough to make the vet happy.