If you tried the proofing activity above, you'll have noticed that it is surprisingly challenging. (You had to know Humour is a name, the different capitalisation rules for the titles, etc.)
It's likely that you failed it first time through, but if you try it a second time you'll get it.
That's kind of the point: while not all proofing activities are that challenging, when they are, then the dynamic of "fail-once-try-again" aids both reinforcement and motivation.