don't worry, 400 out of 940 people will past the test, the most intense part is the interview. Do you even see 100 people here? we are the people that truly care about JMSS, many people around me, in my school or co-curricular that registered for JMSS doesn't even revise much or care much about it. I believe most of us will pass here, due to the fact that many of our competitors are going to selective entries. If you had sufficient scientific knowledge, where a science person usually learns stuff in free time, don't worry, go for it. You might need to revise math, do some numeracy and scientific writing practice ( what I'm currently doing today), what people say are not 100% true, don't stress, studying on exams for 5 or more hours, which is similar to the 14 hours of studying per day in China, is pretty unnecessary.