Last year, my D’s school bill was way more than I had anticipated. I wrote to financial aid office asking for reconsideration with two big expenses we had. (Car repair and medical bill. Without a car my husband would be out of work so it was crucial to fix it.)
The bills were about 4.5k and 3k. I explained each situation and attached the receipts. They reconsidered and gave us more generous financial aid.
You can present your case from the start or wait to see their initial offer.