Thank you for the feedback. The "next level" is like the experience points until "next level" in RPGs where it tells you how many points you need until the next level. So you need one protein for each workout, and you need one workout for level one, and two workouts for level two, so far as you described, it seems to be working as intended though not as clear as it needs to be. There are nine protein powders throughout the level, and you need all of them to max out the three muscle groups. Even without the maxed out jump, you can still get to the "end" of the level in the top right.
I agree, the game needs a lot more work.