Does anyone know what happens with money left over from a federal grant for school?

OK, so I got a federal PELL grant for school this year. So it’s broken up into two semesters and it says the amount you get under each semester. So, if say, I got $5000 for a semester, and I spent $4500, what happens to that other $500? Nothing? Or do I get it back? Or does it roll over to next semester? I am guessing it doesnt….