Comment by Groxx

Compressing accurately requires understanding what's important.

If you understand it that well already, why are you attending a lecture that covers it?

Truly excellent lecturers can often guide some people to that understanding in a note-friendly amount of time, but oh god, most people are not excellent lecturers. The vast majority that I attended were almost literally just reading from the book in class. Book-structured information isn't at all the same as lecture-structured.