How do professors read so fast?

How do professors read so fast?
I wrote a 10 pages essay and my professor graded it in about 5 minutes.

10 pages, double spaced and so on — that’s about 2000 words.

The average reading speed (with good comprehension) is between 250 and 300 words a minute, so 6 ti 8 minutes to read 2000 words.

But a professor probably has upped his reading speed to at least 500 words a minute (there are people who can do way more than that).

Plus, he has a good idea of what to expect in an essay. 99.99% of essays on a specific topic will make exactly the same points and references. It’s easy to see which are missing and any that are not correct. It’s only when you hit a new slant on the topic that you get professors (or any experts) to take much longer — about 1 in 10,000 do.