The Sales Tax Deduction calculation in the Deductions section does not match the IRS Sales Tax Calculator. IRS uses AGI, TurboTax counts all SS Income. How do I fix this?

The IRS website has a Sales Tax Calculator for use on Schedule A, Line 5a. TurboTax is overstating the deduction, causing the Taxable Income to be understated. It is not a huge amount, but it is the wrong number.