Read this thread it explains everything. Everything in there is hypothetical and in regards to your question the higher the rank the better change of you achieving a higher mark, but this
thread will explain everything
In summary though, the ranks are important as it will determine your
moderated assessment mark used to calculate your
HSC mark. When you receive your HSC results they will show a mark for
HSC exam mark,
(Moderated) Asessment mark and the
HSC mark. So if internally (in school) you came 2nd overall and you came first (mark wise) in the HSC exams (i.e. externally) you will receive the 2nd highest HSC exam mark another student has achieved as your
moderated assessment mark and you will receive what you got as in your HSC exam
as your
HSC exam mark then they average these two marks out and that is your
HSC mark
Hope that makes sense