I submitted my amended 2018 return. Does the refund amt on the amended return include the amt already refunded or is it an additional amount to be refunded?

Line 18 on the 1040X would be the amount of refund from the original return and line 21 would be an additional amount of refund resulting from the changes entered on the 1040X. The sum of 18 and 21 would be the total refund from the original return and the amended return. 

Thank you so much!