I don't get the premise. I click the C page [1]. X=c, but what is Y? If you're not going to tell me Y, then shouldn't the page be named "learn X quickly" or something similar?
I think the site's title is just a play on words and generalization of all of the technical books with titles like Learn X in 24 Hours, Learn Y in 7 Days, Learn Z in 30 Days, etc.
To add to this, it'd be nice to have each page with multiple Ys, so you could choose how in-depth you want to go. That's a big ask, though, and it's more of a hypothetical than an actual request
[1] https://learnxinyminutes.com/docs/c/