Your question is vague because your criteria are undefined.

Why do the values "4,6,4" satisfy your definition of peak values? IOW, what does the phrase "peak values" mean -- without any ambiguity.
Why in your second question (2), why do "4,5,6,4" satisfy your requirement?

And not just BTW, not that my reference is to "your requirement." That's quite precise. It's your reqequirement, not ours, and you'll have to define your terms so we have something better than guesswork to work with in our attempts to help (which attempts are never our requirement, but which are done in keeping with the spirit of the Monastery -- to help you learn.