Summer seminar is competitive too. Apparently they chose 600/6000 last year so do your best on the tests. The competitiveness of your app also depends on the other applicants; for example I was accepted to the seminar for USAFA, but rejected to the USNA seminar because the amount of applicants for the USNA is higher as a result of more advertising (from what I've heard). Anyways best advice is: don't worry about a single part of your application, but work hard in all aspects of life. If you focus on your EC activities and neglect testing, you will get a false sense of hope about your application because you think that you are doing good where you are. Remember, you can ALWAYS improve, so instead of asking about how the application works, worry about improving yourself in all areas of life so your application is competitive.