A session is a semester (autumn session, spring session = semester 1 and 2). So if you're doing a 3 year degree it is 6 sessions, or a 4 year degree, is 8 sessions, and your scholarship will cover the whole thing. If you're doing a 5 year degree, it will only cover the first 4 years.
you should have a look at the UTS 2021 Handbook, from what I'm seeing there are autumn/spring/summer sessions which range from 3-4 months (if I did the math right), there's also research sessions (also several months long) but I believe those are for postgraduate students. you should look up the specific course program for the degree(s) you're interested in, then you can work out how long that scholarship is