OK, we can agree, that a children's story will give us 100% comprehension right?
e.g.: A boy went to school. In school he built a paper airplane and threw it through the class. The teacher was very angry and sent the boy home. The boy cried.
Unless you count everything that the author imagined (teacher's gender, country, airplane model...) I doubt that there is a grown-up who would understand less than 100% of these few sentences (unless he is or was illiteral recently).
Now I wonder if some people just always understand much more of a text, if they want to and concentrate. (e.g. I've heard that INTPs have an exceptionally high ability to concentrate)
I often experience the following: We read a text in class, then the teacher asks someone to sum up the last paragraph. However, the part to sum up is often so short, that you can't really sum up but have to just retell everything we just read. And then I think: "Well, why didn't we just read the same paragraph again?"
Now I wonder: Is this something to do with being INTP? Or NT? Or something to do with intelligence?