The amount of the refund that you received from your original tax return should be on line 18 of your Form 1040-X. TurboTax would have put it there automatically if you followed the proper procedure for preparing your amended return. It got the amount from the refund shown on your original tax return. If the correct amount is on line 18, then your refund has been taken into account and the amount on line 20 of Form 1040-X is the total amount that you now owe.
