Can someone clarify this verb as it seems to be quite colloquial in this context whereas it has a different meaning to an English speaker.
The verb “kasuje” means he or she deletes someting. In the infinitive form it would be “kasować”. It could be used in many different contexts, but I think the most important for the word is to delete a computer file for example, or you can also say “Skasuj go” - but it’s only a fun fact, maybe something like an idiom and it means “kill someone”, it’s very colloquial as you noticed. I didn’t glance at the lesson.
I first learnt this word when travelling with my wife in Poland for the first time on public transport. When you board a train or bus often you have to " skasować/kasować bilet" which mean putting your ticket in a machine to validate it. My wife translated it as to “cancel” the ticket, I assume so you can’t use it again. In this lesson it has a different meaning along the lines of punching the prices into the cash register. The cash register itself is called “Kasa” so it probably comes from this word.
Oh yeah, you’re definitely right. It is another meaning of this word, but I think it’s also some kind of idiom. I didn’t even think of that at once. It supposedly, as you mentioned, comes from “Kasa” and my another assumption is that it"s “kasować” because you use it once, and then you’re not able to use it anymore - so you kind of “delete” this ticket.