SAT 2 Biology M Exam

I will be taking the SAT 2 Biology M Exam next weekend. I was wondering how much I should study the body systems. Most sources, like my Barron’s Review book and various websites, say that this information makes up 25 percent of the test, but my teacher says that there are very few questions regarding those topics. If anyone has taken the M exam in the past, can they tell me if it made up a significant portion of the test?

I took the exam in May, and there were barely any human body systems questions, just a few specific ones.

Thank you!