From u/SlytherinAhri, Tales From Retail:

I had a gas pump malfunction today, it quit pumping for some reason and the handle was just all flappy. No biggie, except the woman using it had used all of her reward points and when you hang up the pump, your points are officially used for good. So she had to lose her points in order to switch to another pump. But nothing I can't fix.

So she goes to another pump and pumps 7.5 gallons using her 3 cent default discount. (It doesn't count as reward points, it's just for being a reward member and it's always there.) That means she gets reimbursed for 7.5 gallons with 47 cents off per gallon, because she used her 50 cents off a gallon discount and the 3 cents is a freebie that always exists.

So correct me if I'm wrong, but I multiplied .47 x 7.55 to get $3.55 which is what she would have saved if the original pump kept working and she had been able to pump the extra 7.5 gallons with the 47 cents off that was lost.

Well that wasn't good enough for her and she threw the largest tantrum I had ever seen in my life because "that just doesn't sound right". She kept demanding to speak to a manager and there was no convincing her that I didn't have a manager available. (I'm inside a 14x12 glass box...) I told her she's more than welcome to go to the main grocery store behind the gas station and ask for the manager there but she just wanted me to give her the correct amount of money she was owed. I had to hold the calculator up to the glass and explain the equation to her, but that still wasn't enough. She left threatening me with "I WILL get my points back". Okay good luck lol.

--u/SlytherinAhri