That info is probably a bit old now and in need of a refresh...
Do not fall into the trap of "studying" for it. Most people who do that, end up failing quite badly. There are some books on the Chinese ATP but the one I know is 15 years old now. The questions on the day will be overwhelmingly of the Chinglish variety. That is to say very bad translations of questions from an FAA question bank but increasingly they are writing their own questions also of the very bad English variety. The best thing to do is get a hold of a subscription or buy a Test Prep software. Most agencies recommend and even provide you with a free account to use with:
https://www.feizhiyi.com but it's in Chinese although they provide an English "manual" for you to use to navigate your way around. If you use Google Chrome you can get built in translation which is very helpful. There is also a software you can buy by a company called Dauntless. Most say their questions are out of date but the company claims to have the latest (don't know as of when).
How is it performed? The test is delivered to you by a computer screen at one of the CAAC's testing centers. You have about 3 hours (I think) to complete the test and can skip/return/navigate around the question.
How many questions out of how large a data base? 100 questions, pass mark is 70%. Feizhiyi has about 3000 questions in it's database.
What are the main subjects? Everything as per any other ATP exam. They like to concentrate on Law and Performance based on my experience. On the day, you'll get a big binder with lots of charts and data you will need to refer to in order to answer questions.
Good luck