Once you put in more hours of your day into studying, and stay consistent with it. You end up developing a habit of focusing more on the task you need to do and get done.
There might come a time where you get too tired and still make your self study harder because you said you would study for 8 hrs or 10 hrs or even 16, and you still have a few hours left to get to that mark. Well that is when this chapter comes into play. If you have done the other challenge and now you can study way better than you did before you need to understand something. Since your mind and body and you yourself have gotten used to studying, it is no longer about the time you study. Quality over quantity matters.
Quality over quantity doesn't matter if you still can't make urself study for a few hours (when ur not cramping ofc). This matters when you have the ability to study for long periods of time (because some fields require it) but your thought process due to the first chapters' challenge became "I have to study for 12 hours every day or I will fail"...
The thing is now you have to make sure that you always make progress. Not progress in the hours you study but rather progress on the subjects you are studying for. Progress in your knowledge.
If you study for 12 hrs and you still have your health in check and ur relation with ur family and friends and sleep in check then by all means keep going.(do know you can't always have all those things in check, the things you want in life require you to make sacrifices). But if you dont, then think about this from the first challenge, one thing you should have learned by now is that you can study and obtain more knowledge than you had done 4 to 6 months ago, and that means you don't need to study for that long when you can understand things faster and learn better. You just have to determine what you need to do in this specific day that u are in, prioritize those things you need to do and get it done with the hours you have on hand. If you are very very tired and can't for not even a few more minutes study or work then it's okay let it go, do it in another time or after a break where you have provided a bit or a refresh to your mind.
So for this chapter, the challenge is just understand that quality is way more important than the quantity. Yes I said in the first chapter do a challenge with me and start studying from 1hr to 8 to 10 to 12 hrs but if your way of studying for that many hours doesn't provide you any benefits and you are just sitting there with ur book next to you but not ever actually fully learning anything then thats useless and stupid, it is better to get urself a life rather than keep lying to yourself.