Feeling Guilty

On saturday I went to this stationery shop in Mowbray (next to KFC) to look for magazine folders. The shop had 5 in stock at R32 each. I decided to buy three and gave the cashier/owner R100 note. So he takes out the calculator, says that I owe R66 and then proceeds to give me R34 in change. I contemplated on alerting him to the error, but we had just had a discussion on the price of buying 10 such folders so he was very aware of the price of the folders. I felt a bit guilty esp. as I would have very much complained if the calculation was not in my favour - but then I know my arithmetic ...