Actually, it's probably a translation error. That's a very common way of talking about lists in English and not specific to programming or mathematical subjects.
If I were to ask you to choose a number between 1 and 100, then by definition, the word 'between' would mean that you would not be allowed to choose 1 or 100. Therefore, the word 'between' implies exclusivity. If I wanted you to be allowed to choose the two boundary numbers as well, then I would have to specify that they must be included in your list of available choices. I would have to change my request to, "Choose a number between 1 and 100, inclusive".