Former here (for a point of reference, I had a 7-digit partner number that started with 163)
I used to work at a relatively quiet store. One night a regular came in with her daughter and ordered her usual:
Venti half nonfat, half soy, 3/5 decaf, SFCD latte. She must have been having a rough day because while I was making her drink, she looks over to me and snaps, “that BETTER be three-fifths decaf, I can TASTE the difference.” I glanced over at her daughter who looked at me and mouthed the words, “no she can’t.”
That night and every time I made her drink after that, she got 2/5 or 4/5 decaf and never had any idea