Kelly states that she used a counterfeit detection pen and it made a yellow mark on the bills, which she took to mean that the bills were genuine. The rest of the staff tells her that the opposite is true, that genuine bills will show a dark mark. This is incorrect. Counterfeit detection markers leave a light mark on genuine bills and a dark mark on other types of paper.
When Amy assigns Kelly to register duty, Kelly states that she's never worked the register before. In Sal's Dead (2017), Amy cut Kelly's break short, in an effort to keep her from communicating with Jonah, by assigning her to work register 4. At that time, Kelly's only complaint was that she hadn't eaten her cup of noodles yet, not that she was unfamiliar with how to work a register.
Bo puts the store over the amount needed to become Quad-A by purchasing a hot tub, but this happens before any money from Glenn has changed hands. Given Bo and Cheyenne's ongoing money struggles, there's no way he should have enough money to front the cost of the hot tub himself, nor would someone as young and financially irresponsible qualify for enough credit to make such a purchase.
Even if business had picked up there would be no way that they would be able to make $80,000 in the span of a business day.
Both Kelly and Mateo refer to the TV a customer is checking out as a "4K TV." The Cloud 9 fact tag below it lists it as 1080p resolution, not 4K (2160p) resolution.
In the Crestwood store break room, Angie is seen smoking. Smoking in indoor businesses is illegal in Missouri.