Maybe he is not overfeeding the dog.
With lower quality dog foods, you have to feed more.
Here are the feeding instructions:
PEDIGREEĀ® Dry Dog Food | Adult | Complete Nutrition | DRY
So, let's say that Balboa is slightly overweight and that his ideal weight should be 35 instead of 40 kg. Thus, a 77 pound dog should eat 3 1/2 to 4 1/2 cups a day. So, the dog needs to lose weight, let's try feeding him 3 1/2 cups, which makes 28 oz, which is 794 grams. The OP is feeding the dog 100 grams less than recommended already.
I would be really concerned about possible health issues.