Why is the sequence "3,3,4,5,2" considered a bitonic sequence?
The words "increasing" and "decreasing" are used in inconsistent ways. Probably, you're assuming one definition while the author of the text that's confusing you is using the other.  Say that the sequence $a_1, \dots, a_n$ is


type&nbsp;A if $a_1\leq a_2\leq \dots\leq a_n$;
type&nbsp;B if $a_1&lt;a_2&lt;\dots&lt;a_n$.


The problem is that


some people refer to type&nbsp;A sequences as "nondecreasing" and type&nbsp;B sequences as "strictly increasing", which is unambiguous;
some people call type&nbsp;A "nondecreasing" and type&nbsp;B "increasing";
some people call type&nbsp;A "increasing" and type&nbsp;B "strictly increasing".


This means that the term "increasing" is ambiguous because some people use it for type&nbsp;A and some people use it for type&nbsp;B. (And ditto for variants of "decreasing".)

The same problem occurs, though to a much smaller extent; with the terms "nonnegative", "positive" and "strictly positive": the first definitely means $\geq 0$, the last definitely means $&gt;0$; the majority of people use "positive" to mean $&gt;0$ but a few use it for $\geq 0$. (And ditto for variants of "negative".)