I feed the dog, not by the print on a package. If the dog looks good I'm happy. If he looses weight, I up the quantity. If he's getting pudgy, I cut the amount.
Every dog is different, as is every person. If I ate like my husband, I wouldn't fit through the door! Some dogs and people need more food to maintain a decent weight. Some need less. What is printed on the package is just a recommendation, not a rule.
It sounds to me as though your dog is doing fine on the amount you are feeding. Keep doing what you are doing and adjust when necessary.