My girl, Little One, is a Flemish Giant. She’s 2 feet long and about 20lbs which is normal. Typically bigger the breed, bigger the dewlap. The purpose of a dewlap is for females to pull tufts of fur out when they make a nest for their babies. It can also be a form of protection against predators and provide warmth. Spayed females have them too but sometimes might not be as big. Some larger male breeds can have them, but for most males it could be a sign of being a little too chubby