I'm not sure how the online offer algorithm works, but I reckon it goes like this.
Starting from a student with 99.95 atar scores,
Checks their first preference,
If offered, end.
Else, checks their second preference,
And so on till an offer is made or the end of their preference list.
Then, it moves on to the second 99.95 and repeats the same process.
One the set of 99.95s is finished, the code performs the same thing on 99.90 and so on.
Each course has a limit place on it, so once the limit has been reached, offers won't be made forint anymore.
If the code works this way which I believe it does, first or ninth preference won't affect you chances. But the code can also work in a way that instead of going down the preference list of individual students once at a time, it offers all first preference for that set of atar scores first, then moves on to the second preference for that set of atar scores. If this is the case preferences will affect you chances, but you must be really unlucky for someone with your atar score that gets the offer while you don't. I'm also inclined to think that if this is the way it is coded, there would be a condition stating that if an offer is made to that specific atar score, the system will offer all other students of that atar even if the course is full. This is so that the cut off score will be the same of all students.
Note that this is all speculation by me and how I would code something like this. (Ofc factors such as pre-req, bonus score from specific subjects,seas and stuff would be included too)