Your preferences work your way down through the order. For example, if you do not meet the requirements for your first course they will then look at your second, then third etc. It doesn't disadvantage you if its third on the list of first, you will still be judged equally.
You have nine preferences, I don't know about you, but I made sure that my ninth (or last) was something I would definitely get into. It was my safety university.
I got the offer I wanted in the late round last year, but that was partly because I sat UniTest.
Some universities and courses "inflate" their published UAI and therefore people with lower UAIs get in the late rounds. For example I knew a handful of people who applied to UC with UAI's around 5 points lower than the published cut off for that year that still got into the course they wanted in the late rounds. I think this is much less common for the better/more desirable universities.
To be honest, I am firmly of the belief that if you don't know what course you want to do before you go to university then you probably shouldn't be going yet. I see these people with six different courses, sometimes quite unrelated, and I wonder what the hell these people are doing. If you don't know what you want to do now, its unlikely that when you finish the degree you weren't sure you wanted to do you'll actually want to work at that field for the next god knows how long.
Until people firmly know basically what they want to do I think they should take some time off, maybe do some work experience in relevant fields. Its perfectly fine to change your mind while you are doing uni, but you should at least start with a direction. Its thousands of dollars and years of time, but a lot of people these days are more interested in the money university could bring them, rather than actually enjoying their lives.
Sorry - ramble. My point is that if you chose a first preference and then hours later decided you definitely don't want that then I think you should evaluate whether you should go to university right now, because you don't want to do a course for six months, regret it all, transfer, be behind, fail, fall into debt and drop out.
You can get offers in the later rounds though, not from all institutions and only from the courses with available places.
