10 days is a pretty short time to prepare, and since you haven't given many specifics about what you've already studied, I apologize if what I say is useless. From my own experience, I found that scores can be brought up rather rapidly. When I took the test last year, I studied every Saturday and Sunday for one month (eight days if you add them all up); from these weekend study sessions, my score increase by about 200 points from a 500-something to a 780 (so not objectively great, but a big improvement from where I was). I didn't really do anything particularly special except take a practice test, review my errors, and then write down the equations I wish I had known. I'm guessing you've already taken all of the practice tests, but if not, then this is what I'd recommend.