The amount withheld on your W-2 and the amount you paid in estimated taxes are tax payments.  Each type of tax payment is entered on different lines of your federal tax return.  The TurboTax software will correctly enter the tax payments if you use the proper sections of the program for each type of payment.

Enter your W-2 in the Wages and Income section under Federal Taxes.

To enter, edit or delete estimated taxes paid (Federal, State, Local) -

• Click on Federal Taxes (Personal using Home and Business)
• Click on Deductions and Credits
• Click on I'll choose what I work on (if shown)
• Scroll down to Estimates and Other Taxes Paid
• On Estimates, click on the start or update button

Or enter estimates paid in the Search box located in the upper right of the online program screen. Click on Jump to estimates paid

Your example means that you have paid in $7200 to apply towards your taxes for the next year.  Technically your withholding is $6000 and your estimated payment is $1200.  So saying you have $7200 withholding is not technically correct. 

Look at the form 1040 ... see how it works ...