I’m not sure any human being with no superpowers can actually ever be able to comprehend all the words in SSiW listening practices!
I was puzzled too, I think the answers I received might be useful to you as well (see link below in this post).
In any case I can tell for sure is that when I started Level 1 I was able to identify something like…10 or 15 words here and there in all.
But I just listened to them again and now I can catch 100% of the first (the one at normal speed) and 70% or even more of the faster ones (except practice 5 that goes way lower than that).
It’s not as bad as it seems at first, it just takes a little time to get used to it!
But most of all, that’s not the point of the exercise anyway so I wouldn’t worry too much. 