Generally speaking, the amount of white on a Pied is random and not related to the amount of white on the parents.* Two high whites will throw low white babies and vice versa. That is, if both parents are just plain ol' Pieds.

Combining pied with other genes can and will affect the amount of white the resulting babies have. For instance, Enchi Pieds tend to be lower white, while Spider Pieds are very high white.



*There may well be modifiers that influence the amount of white. But unless you're line breeding, it's probably not worth chasing them.