I don't really believe that it's 4, because doing research that's what I found as well and found it hard to believe considering about 50 US applicants are accepted per year. Anyway, I had my counselor email the cambridge assessment center with the details they ask for. If you do a quick google search you should be able to find the instructions. Basically, they will give your counselor a log-in and password and then she can register you for the test. It's very straight-forward.