3-5 section. the section is actually just 4 sections to UNSW from central so if you're really desperate and only have a 1-2 section ticket just use the 1-2 section twice.
to be honest with you, i have seen those people who hop on the buses to check whether they are using the right tickets. Usually happens sum time during the arvo, but its on occasion that i have seen it. I didnt really see those 'people' everyday though... just something to keep in mind though just in case they pop up on the spot.