Pet quality        In your post you called the puppy pet quality.  The amount of white on the puppy's chest will not make a differance in the amount of love that it can give to you- or you can give to it.   
If you are wanting a puppyto show and or breed it might make a differance. Many YT have white on the chest it is quite common. This white is masked as the other coat grows long and covers it. If a breeder has a concern as to the amount of white on the chest- thay may grade the puppy as pet/companion quality.   
Wnalegria     |