What is supposed to happen to the leftover Pell Grant money at the end of the school year?

I was awarded a Pell Grant up to $5000 for the 2009 – 2010 school year. I have received about $1000 total for the last two terms. I got half time and half the $1,400 last term and and only less than quarter time this term. I thought that the money that’s not used gets pushed back every term until the end of the school year. Not what financial aid told is happening, which is that “the money I don’t use gets distributed to other students”. I have NO CLUE what that means and I’m really frustrated. I feel like I have to go full time because I don’t want to waste the money.
I can’t take any classes until the fall because I’m waiting to get into a pharmacy tech program. I’ve spent almost a year working on this and I’m really not sure that everything is right. I know this is specific, but I really want the best answer. Thank you.