Change is a good thing, but still...

For lunch today, I stopped into a place here in Stevenage and bought a roast chicken bake, a packet of crisps, and a Diet Coke. My total was £2.30. I handed the cashier a £10 note and she gave me £8.70 change. (Do the math...)

I said, "Oh no, I was supposed to get £7.70 instead...," so she handed me (another) £5 note.

Once again, I said, "Oh no, I was supposed to get £7.70 instead...you gave me too much."

Ever gone to lunch and had a chance to make a £6 profit?