A peke pup at that young should be a pound or maybe 2. My pup is 11 weeks old and 3 pounds. There's no way that this puppy will end up between 7-10 pounds. At 6 pounds this puppy will be a lot heavier when full grown. It looks like they lied to you about the parents.
Do you think that maybe they meant the Mom was 7 pounds at eight weeks old and the Dad was 10 pounds at the same age? I have a full grown, full breed Peke & he is 21 pounds at 7 years of age. He is not fat & I got him when he was 1 year old and he was around 17 lbs. I would think that he probably was a good size puppy, because they grow quickly it seems and then slow down and he was 17lbs by one year old. Jus saying : )