"There is a capital loss carryover amount on the tax return that you did..."
Just to be clear here, you prepared your own income tax return and you are responsible for its accuracy. TurboTax simply "rented" you the software to allow you to prepare your own income tax return. TurboTax's "Accuracy Guarantee" basically only extends to faults in the software, it can't guarantee that the numbers contained in the income tax return are correct.
"...I want to know how you arrived at it if I did not due my taxed through Turbo Tax for 2017."
So it appears that this conversation involves a 2018 income tax return and by your reference to "2017" I assume that you are referring to a carry over that came from 2017 or before, not a carry over that will now be available in 2020? And when you prepared your 2018 income tax return you didn't transfer information from a 2017 income tax return prepared using TurboTax?
If that's the case then the most logical explanation for that is that you entered that number as part of your input. There is an interview titled "Capital Loss Carryover" that's in the "Investment Income" section under the "Wages & Income" tab.
