You won't be eligible for ANY Federal or State financial aid for 1 class, you MUST be at least half time to receive ANYTHING. And if you're getting Pell grant it is cut by half when you lower your credit hours to half time.
You must be taking at least six credit hours to get federal financial aid. To receive the "full amount" you must be attending full time, which would be a minimum of 12 credit hours.
Refunds vary from a few dollars to a couple of thousand.