Acustomer complains that he was short changed by you receiving only 13 cents change from 2 dollars instead of 31 cents. what would you do

We are asked what to do when we are the cashier in the grocery and we are facing a situation on which we gave 13 cents change from 2 dollars to the customer instead of 31 cents. The best thing to do is to relax and stay calm, approach and talk the customer politely. Then you can ask an apology and add an additional amount of 18 cents to complete and give him the correct amount of change.