I'm 17. how bad on a scale of 1-10 is a blood sugar level of 315?

Forgive my frankness: Forget the "scale of 1 to 10". I am going to assume that that this is not a lab error, something drawn while you were gravely sick, or drawn from below an IV infusing glucose. If I'm right, and it's mg/dL, then you have diabetes and you are very seriously sick. If you value your health (brain, feet, not being in serious pain) in fifteen years, manage your disease like an adult.