brunopalermo, the manual says exactly this, simple logic dictates that in a list: 1,2,3,4,5; the numbers in between 1 and 5 are: 2,3,4. This is always the case. If one is going into programming anything, even in C2, they should learn this kind of thing first. If you wanted to test if a number was between two others in programming, using this example, it'd look like this:
This will always be the case. If you were sitting next to a friend, sat a cup in between you two, and someone asked what was BETWEEN the two of you, would your answer include you and your friend? Of course not. Your answer would only be the cup. It's not very complicated.