Since you have approx 4 months left, and you obviously have some free time, I personally would concentrate on some other things.
1. Spend quality time with friends and family, and make some good memories to hold you through the hard times
2. Pick up a copy of the blue jackets manual (or look on the internet) and memorize the general orders of the sentry, Navy and other service ranks and insignia, and if you still have free time, do some math review. Quite honestly though, the Navy will teach you all the math you will need for the job you are about to do.**
3. Go run. Get yourself in shape, if your not used to (I wasn't) the PT can be brutal.
4. If possible, as the weather gets colder, try to acclimate yourself. January at Great Lakes can be harsh.
Hope this helps, and Have a day
-Matt
**Not to disparage the advice others have given about material to study, just my opinion that the time might be better spent concentrating on other aspects that you may not have been exposed to yet. I assume that with your Associates degree, you have already received some higher level math instruction, and the Navy stuff doesn't get much above entry level calculus. Most of it is basic algebra, physics math, and conversions.