I wouldn't do 1 cup. But 3/4 doesn't sound too bad.
However, he's young - if he's hungry, I'd let him eat.
You can start worrying about extra pounds once he's full grown around one year or so. Every dog is different and you will learn what they need to satisfy them. OR some dogs will just eat and eat and eat even if it's way too much! LOL. So you just have to know your dog.
Jackson is 3, very active, and eats 2/3 cup per day of kibble (at 430 kcal/cup) and gets a few treats and a bit of wet food too.