What-If form 2024 Balance Due different $ than tax return

Love the What-If form functionality.  Used it to calculate prepaid tax for 2025.  TurboTax What-If first column line 72 balance due is $315, whereas the Federal Tax due at the top of my 2024 return is $449.  Since Turbo Tax imported the 2024 return into the What-If form why is the balance due amount different?