"but there should be a credit to the taxpayer since that money was really not owed up to $10200"

Yes; go to the bottom of the 1040 to see amounts paid in against what is owed, or what will be refunded.

You seem to be looking for this in the wrong place. Or, thinking about withholding incorrectly. It isn't against what you owe.

It's the IRS making sure you Prepaid for something that you likely will owe for, once you file your tax return. Then, your Tax Return is your entire Financial Life, and that is the reconciliation for what was prepaid by Withholding and Estimates, against the reality of your tax year.

Once you paid in, there is no Adjusting it. It's Paid, already. That isn't Taxes. It's a Payment against taxes.