The app is not calculating my “Tax Liability” accurately. Total taxable income multiplied by the tax rate of 11.3%, off by about $25. Which increases my refund. Help.

There is no 11.3% rate.

That rate is just an approximate/handwaving number.

Your actual taxes are calculated using either:

the IRS Tax tables

or

one of ~ 7 different tax calculation forms, depending on what types of income were in your tax file.

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At this point in time, there are no known Federal tax calculation problems  (but it is early).

IF..(big IF)  if you have a simple tax return, with just ordinary wages and simple interest,  that only uses the IRS tax tables (and  no Self Employment income, no qualified dividends, no capital gains or losses)

Then, you take your "Taxable Income" (line 15 of the Form 1040), and compare it to the IRS tax tables to get the tax that the IRS will assess:

Publication 17 (2024), Your Federal Income Tax | Internal Revenue Service

It depends what kind of income you have. Even though the full amount shows up in the total income on the 1040 line 7, if you have capital gains or qualified dividends the tax is not taken from the tax table but is calculated separately from Schedule D. The tax will be calculated on the Qualified Dividends and Capital Gain Tax Worksheet. It does not get filed with your return. In the online version you need to save your return as a pdf file and include all the worksheets to see it.