Maybe they haven't actually weighed the mom and dad and are just guessing? Or maybe flat out lying? I know my chi Harley's mom supposedly only weighed 3 lbs - but let me tell you, that was the biggest and heaviest 3 pounds I've ever seen! (DH and I guessed she was at least 6 lbs). Sometimes people alter the truth a bit to get people to at least see the babies and fall in love.
I hope that poor mom is bigger than 2 lbs.
It just breaks my heart.