Impossible to even guess without knowing about how strong your cohort is. If you've got a pretty bright cohort, you can get a 30 with scores as low as 60% and a decent exam day performance. I was floating around the 50% mark in nearly all my SACs in VCE, but had a very strong cohort backing me and I did slightly above average on the exams. I wound up with a 33 raw. On the other hand, you might have a not-so-strong cohort, which means you'll have to distinguish yourself from your peers a bit more to hit the 30 mark - potentially you'd need SAC %s as high as the 70s/80s.
Your best course of action is to try not to spend much time working out what minimum standard of performance is required from you to meet a certain ss goal, and spend that time doing the best you can right now. Setting goals and standards for yourself or trying to work out where you are at the moment can be helpful, but it's nowhere near as helpful as actually doing work is.