I am not sure what it means when asking for the vehicle total cost, i traded in the car in 08/2020.

When it refers to remaining basis, it is asking for the trade in allowance of the old vehicle.  The depreciable basis of your new vehicle is the cost of your new vehicle minus the trade in value of the old vehicle  By providing the trade value of the old, Turbo Tax will correctly determine the depreciable basis of your new vehicle.

Are you able to provide me with an example please?

New vehicle      $20,000

Trade in value    $3,000

Depreciable basis of your new vehicle=$17,000