Deductions & credits

OK here is the problem.

The first time through I entered a $75 amount in the ACA deduction area (no Schedule A) now I cannot get back to it. I went to Schedule A as you recommended and entered $95 but it will not update the ACA $75 amount and I get no error check because the total is under $300. How do I get back to the ACA Data Source to eliminate it so the Schedule A Data populates that ACA field?