Say you’ve got 70 actual scenes. It doesn’t matter, really. There’s no magic number. The point is, you have a limited amount of time. 70 beats looks like quite a lot, until you try to fit everything into them.
You have to choose. Say one of your big beats is that your protag with Asperger’s syndrome demonstrates empathy for the first time. It’s a focal point and a serious shift in the story.
How many beats do you give that setup and payoff? What is the best way to show it?
I have no idea, it’s your story. But I know that you want to organize your thinking this way to create the moment for me as poignantly as it exists for you. That means you need to run up to it for thirty beats, knowing it’s coming, showing me what it’s going to mean for this protag when it happens.
Write with that point of reference. What is going to make that moment resonate most? What can you use? Is a surfer or a veterinarian a better choice as a supporting character? Rebuilding a transmission or planting a garden? Getting into college or falling in love? What’s the nature of the main source of friction? Parents? The tough kids? What happens when the protag fails to feel empathy? Job loss or friend loss or legal trouble?
They’re all choices. You don’t have time to develop them all.