Turbo Tax is a self prepared return. They only guarantee the calculations based on the entries you made. They don't know if you entered something wrong or in the wrong place or left something out.
I would check over your return and see if you can see anything wrong especially in the payments section. Make sure you agree with all the amounts listed. Like is the difference the same or close to the refund you got last year? Maybe you put down that you applied last year's refund to this year? Or you applied part of your refund to next year as an estimated payment. Or you put down you made a payment with an extension or paid an estimated payment that you didn't make?
A common adjustment is if you claimed the Recovery rebate credit on 1040 line 30 when you already got the Stimulus payment or got the second one after you filed or reported the wrong amounts or entered them in the wrong box. Do you have an amount on line 30?
