The 10% was tax withholding on the distribution, not the tax liability you incurred by taking the distribution. The the effect that the distribution has on your tax liability is not determined until you prepare your tax return because it depends on how much other taxable income you have on your tax return. Tax withholding is simply a prepayment toward the overall tax liability determined on your tax return. The tax withholding is credited on your tax return toward that tax liability.
If your distribution qualified as a coronavirus-related distribution, TurboTax is not yet able to fully calculate your 2020 tax liability because Form 8915-E for reporting this distribution is not yet available. You'll need to wait for this form to be implemented in TurboTax.
