Following the link might help, but I believe the general idea is that if you're trying to present information in a graphic, to sort out what is important about it and what presentation will make it clear.
If you're trying to present any kind of information at all, you should figure out what is important about it and what presentation will make it clear.
Unfortunately, the quote above isn't at all clear, even in context. I suspect this is because Jacques Bertin isn't as good at expressing himself in English as in French, but even so I'm unable to understand the sample data he presents or how it relates to the point he was trying to make.
Here's the new quotes thread, for all those quotes you were going to post.
Rules: