Here's the Errata page for the 5th edition:
https://www.manhattanprep.com/lsat/errata/There doesn't seem to be a typo on pg. 42, though.
If I had a rule, 'K before N", written
K -- N
I can infer that
N can't be 1st
K can't be Last
So if we had 6 spots, I could write a ~N under spot 1 and a ~K under spot 6.
The rule we have is
K _ N
The earliest we can put K is 1, so the earliest we will see N is 3.
Thus, N will never be in spots 1 or 2. The diagram is saying underneath "N can't be in 1. N can't be in 2"
Similarly, the latest I can put N is 6th, so the latest I can put K is 4th. That's we see "K can't be 5th or 6th" under the diagram.
Make sense?