I know it can be confusing.. lol I just kind of estimate. Depending on the type of food you use, just estimate how many of them would fit in your turtles head, (say if it were empty). I feed my 2 -1.5 yr old turtles approximate 10-12 sticks every OTHER day. Along with veggies of course. Just depends on the size of your turtle and it's head. Oh, the part of the head is just the head not including the neck.
I've never gotten a definitive answer on what amounts others come up with so it's kind of a guessing game..
But it's safer to err on the lesser amount than a larger amount due to the high protein in pellets.