The amount is the total of all distributions to an income or expense account without a tax line assignment. Check the transactions from which QuickBooks calculated the amount; you may find that some transactions distribute to an account that should have a tax line assignment.
The accuracy of the tax summary report depends on whether each tax-related income or expense account has the appropriate tax line assignment. QuickBooks uses the assignments to calculate the amounts to report on individual lines of your federal income tax forms. For example, if your Telephone expense account is assigned to “Schedule C: Office Expenses,” QuickBooks includes all amounts distributed to your Telephone account in the total shown for “Schedule C: Office Expenses” in the tax summary report.