Generally, USNA approaches the CFA as a pass/fail event. However, you can get a small number of "bonus points" for extremely strong scores in certain areas, such as pullups. Conversely, extremely low scores in certain areas can hurt you a bit (even if you pass the CFA).
Historically, the focus has been on upper body strength because there is apparently data that shows that candidates with good upper body strength (as measured by the CFA events) are more likely to do better physically at USNA. However, recently, greater emphasis has been placed on running at USNA. Not sure if this has translated into admissions yet.
However, if you are serious about attending USNA, work on improving your run time starting NOW. Your time will not be satisfactory at USNA. When I was there, men had to complete a mile run (after pullups and situps) in 6:30. Now the distance is 1.5 miles and the max time is something around 10:00. So you can see that a 7:51 in the mile won't cut it.
I suggest talking to the track coach (or any gym teacher) at your high school to develop a plan to improve your running over the next four months. An organized plan will, in my opinion, help you much more than just trying to do it yourself. Trust me, you do NOT want to be out of shape in terms of running when you report for I-Day. Whether good or bad, accurate or inaccurate, early on you are largely judged by how strong a runner you are.