My chihuahuas only eat about a 1/2 cup every other day. So that is about 1/4 cup aday for each of them. You must realize that there little bellie aren't that big and will not eat alot at one time. When they are that little i always free feed them until they are at least 6 mos of age. And you know what that means alot more bathroom brakes. because when you free feed one you have to kind of watch them and when you see them get thru eatting that means that you have to take them outside right away.
The bag always tell you more them what that they should eat. And as long as he is eatting about a 1/8 to 1/4 cups aday i wouldn't worry to much about it because they have little bellies.