Adjust the font a little bit, add two spaces instead of one between a period and the first letter of the next sentence, and try to add in some analogies.
Maybe even substitute some words for bigger words, and if there's a title you can add a little more space between the title and the first paragraph.
I would say, maybe ten points might be taken off your grade. That's just a guess though, I figured ten points for each page. But if you did the best job that you thought you could do and still didn't make it to the ten page mark, I would definitely make a note of that on a Post-It and attach it to the paper when you hand it in.
One thing I've learned in college is that a lot of professors "up" the page limit by a few to make us students expand and challenge our thinking process. But a lot of times, like in your case, that might end up hurting our grade than helping it!
Good luck.