The "spreading" of the tax withheld is automatic in the IRS calculation of any possible penalty. It's not shown explicitly in TurboTax or anywhere on the tax return. The tax withheld is not treated as quarterly estimated tax payments. It's a whole separate category. The only hint you will see that it's treated differently is that tax withheld is on Form 1040 lines 25a through 25d, and quarterly estimated tax payments are on a separate line, line 26.
