Yeah, the word they were looking for is "markup". People make this mistake all the time.
Once when I was in an RPG shop I visited frequently, some youths came in and said "We want to order 5 figures." After a short pause they added "Can we get them cheaper, because we're buying 5?" The shop owner said "Fine, I'll give you one for free." They said "No, the other owner promised us 10 percent". After a small pause the shop owner smiled and said "Ok, I'll stick with the promise, you get 10 percent."
I've come to see the use of percentages as a warning sign.
"markup" versus "margin" is an arbitrary choice, not something people should be expected to intuit. And they're usually close in value, so people are less likely to be informed or reminded of the two terms and which is which.