I'm married with a 20 year old college student . I received both rounds of stimulus but TT says I will be getting an additional 1200 . Does this seem correct?

No, based on what you are staying, the amount does not appear correct. 

The TurboTax software adds together the entries that you made for receiving stimulus check 1 and stimulus check 2.

The software computes the amount of your stimulus check amounts based upon the information that has been entered into the tax software. 

If you are due an additional amount, it will be issued as a Rebate Recovery Credit (RRC) on line 30 of the 2020 1040 tax return.

I suggest that you review your input on the rebate recovery screen

To review your stimulus payments on your tax return:

1. Login your TurboTax.
2. With your return open, search for the term stimulus.
3. Select Jump to link.
4. Under the combined total first-round stimulus payment enter the amount you received.
5. Under the combined total second-round stimulus payment, enter amount received.
6. Click on Continue.