i can choose from 2-8129 i think, but its 32 (default)
anyone willing to explain if i should change it and why i should or not?
It depends on what you are using to mine as some difficulty's work better than others, and also depends on your hashing rate also.
If you could provide some more info or search the forums and you will find other people may have posted optimum settings, those settings wont always be the best for everyone but you could use them as a rough idea.