TT calculates it based on what it knows, if it didn't have correct 2023 AGI/Tax info (carried over or input), or estimated tax amounts/dates etc then it will calculate a different result from IRS. IRS calculates it independently based on the information in their systems. See Form 2210 lines 1-9 for the safe harbor calculation. You can check details such as estimated tax payments from your account at irs.gov.
