Solve the problem

Today, my part-timed worker was saying the prices of the items and I keyed them on my cash register. An item cost RM30.80 but I heard RM36.80. 

When my worker pointed out my mistake, I minus out RM6. Towards the end, the rice cost RM13 but I mistook it for RM15.

When I had printed out the receipt, my worker went through the list and pointed out that I had keyed in both RM15 and RM13.

Yeah, I admitted my mistake and so I refunded her the RM15.

But this customer was not happy. She wanted me to recount the whole items.

I just asked my worker to say the prices of the items while I checked with the list.

About 40 items being checked and it was alright. 

I gave back the correct change to her and the problem was solved.