The short answer: we can't tell you, because it hinges on so many factors.
To put it simply, we have no baseline for comparison as 93% at one school might be as good as 5% in a SAC at another school by virtue of SAC moderation. The most important thing, therefore, is the rank that you have in your cohort. Further, your performance in exams in maths subjects is hugely important, as they make up more than half the study score.
I'd advise you to do a bit of research to understand how SSs work for yourself -- it might be worthwhile to look at VCAA's grade distributions and check out this thread on how SAC rankings work.
Grade dist -- match up previous exam scores with grade marks:
http://www.vcaa.vic.edu.au/Pages/vce/statistics/2015/statssect3.aspxHow SAC ranks work:
{SAC RANKINGS} -All you need to know about it-Have a nice day.