[abdullahkhalids]

Understanding is not binary. They mean that the bright student walked away understanding X% (maybe 70%) of the major logical steps Von Neumann made.

Those students could then go home, open a book or the transcript of his lectures and spend 5-10 hours figuring out all the details, and exploring auxiliary stuff not covered in the lecture.

Lecture time is fixed, outside-lecture time is 10X lecture time.