Words out of reach, that you cannot grasp

Out of reach in this context mean words that are out of my ability to remember?

I'm not sure what is "grasp" in this context, any help please?

(At 3:22 relevant part) And, I also want to test you now. I now will show you 15 words, you'll have 20 seconds to memorize them. Please try as hard as you can as if it would be an exam. And after those 20 seconds, we will see. Time starts now. Try as hard as you can. You still have 10 seconds. Look at all the words, however you want. Five seconds. Three. And ... Time is over. Now see how much you can remember. Really try to find all of the words in your head. Go from one to the other. And what I can tell you is that some words might come easily, some might take some time, and some might not come at all. Well, it might feel like you might get seven, eight or nine words, but there are still some words out of reach, that you cannot grasp. And I did this to illustrate that it's an effect that you get in school, in university.