My guess is this is an honest mistake. I was the head coach at a school that did not stack scholarships (meaning you choose between and athletic or academic but you could not receive both) that was easy for The coach to figure out.
Example:
Tuition, room, meals and fees 30,000.00
Athletic scholarship 12,000.00
Athlete pays 18,000.00 plus books and the occasional lab fee
* note: if you have any federal assistance FAFSA - deduct that from your total owed
Your situation for the coach is a little more difficult. I also coached at a school that stacked scholarships. This is where a coach can make honest mistakes (probably what happened in your case) by trying to be too helpful. He/she most likely projected your academic scholarship to be a certain amount and it appears he was wrong. It would be best practice for a coach to state this is your athletic scholarship and that is what I control, what you receive via academic scholarship will come from admissions and you can refer to them for that amount.
If the 5,000.00 is too much for you to pay and you have decided if you are required to pay that you will not be able to attend college ask your coach for a release and explain why you want to release and back it up with emails. most likely he would release you. If not, take it to the athletic director to get a release if that is what you want
Good luck