wow your results are so great!! does this mean someone that ranked maybe top 10-15 but say got a mark in the 60s can still do well in HSC due to their rank, despite really bad results?
I'll give you 2 extreme scenarios to illustrate that your raw internal mark doesn't really mean much.
Case 1:
Everyone in your cohort is super smart but your teachers were feeling mean and decided to set an impossible paper and mark it harshly. Your mark in the 60s is actually an amazing achievement - it will translate into a very good HSC mark.
Case 2:
Your cohort isn't great and the teachers marked very leniently to boost morale. Lets say the top mark was in the 80s but your teachers know that the top student might crack a band 3 if they're lucky. Your 60s mark probably translates closer to a 40s mark.
Usually case 1 is the case, as teachers often mark a lot harder than the HSC (after scaling/alignment). Case 2 is so extreme that it probably doesn't happen at all.
All you gotta do is work hard for the HSC to maximise your possible score. What's done in school is done, so all you can really do now is prepare for the HSC as best as you can. Don't get caught up in the whole internal marks business as there's nothing you can do to change it now.