Hi, We recently adopted a puppy from someone who had no information on her whatsoever! The girl we adopted from had her listed as a "lab mix", and thought she was about a year old because she has all of her adult teeth. She is the sweetest most loving puppy in the world! Because we had no info, and wanted to make sure she was healthy, we took her to the vet the very next day. The vet said she definitely see's some lab, and some pitbull, and she said that she believes she is around 7-8 months old. But, she is just over 20lb! Isn't that very small for that breed mix? Could she just be small for her age/breed, or do you think she might be mixed with a smaller breed too?

That's the thing with mixed breeds, unless you saw both parents you never REALLY know what's in there, even then it can be a toss up.
It could also be that she just didn't get a good start in life and has some catching up to do.
If your vet thinks that she is in good body condition and developing well, I wouldn't worry too much about her size.
And at 7 - 8 months she still has some growing to do.
Just enjoy her and feed a good puppy food to ensure that she gets all the nutrition she needs.
And of course keep up the check-ups and vaccines, that will be very important to her health.
And thank you for adopting, they all deserve a loving home and it seems your girl lucked out.

I agree with Lady Sam. Often neglected dogs are smaller than they are supposed to be but once you start feeding them they shoot up. I also have noticed bully breeds get their teeth quicker than most other dogs.