Recommended feeding guides are always per day, divide the daily total by the number of meals. You can feed a 15 week old puppy twice a day or three times a day, it's up to you. I fed both my dogs twice a day from 9 weeks old. I did do a lot of short training sessions using healthy treats between those two meals, so it wasn't like they had to totally go without food for 12 hours.
Unless your food is an all life stages food that gives you feeding guidelines for puppies, you're probably looking at the recommended amount of food for a 20 pound adult. Young puppies need more calories and should get 1-1/2 to two times as much food as an adult dog of the same weight, which should be adjusted as their growth starts to slow and they near their adult weight.
I do use the bag guidelines for feeding quantities, but as a guide only - keep a close eye on his condition, you should be able to feel his ribs easily and see the last one or two. If he seems overly skinny (you can see all his ribs), increase his food. If he's starting to get a bit chunky and developing some padding on the ribs, cut back his food slightly.
Like Tracy, I have a dog that would eat until he exploded. Keefer has always been that way. Free feeding would be a disaster, even as a puppy!
I've also had dogs that weren't that interested in their morning meal but would eat lightly. As long as they're at a healthy weight there's nothing wrong with not dividing the daily total exactly in half and feeding a bit more at one meal than the other.
Edited to add: Ah, I see he's on a puppy food, so the bag recommendations are for puppies. Obviously.