The mark itself doesnt have much significance. The original raw assessment mark your school sends in and get moderated according to how your school scores in the hsc.(simply)
In more detail if your interested, say you rank first with a raw assessment mark of 60, say someone else scores 95 in your grade, your moderated internal assessment mark will be 95. Although if your ranked in the middle, it gets complicated, with BOS using your grade's mean, and a correlation of how your cohort performed in the actual hsc exam and the ranks that were sent in originally to give you your moderated assessment mark.
It is your rank, and the gap between ranking that matters.