so how do they differentiate between people if they got the same final HSC mark?
If students are equal on the highest HSC marks in a course, then the following process is used to determine the recipient(s):
take an average of each student's examination mark and assessment mark after alignment to performance bands, each to one decimal place
take an average of each student's examination mark and assessment mark before alignment to performance bands, each to two decimal places
if an extension course, use the marks awarded for other courses in the subject area.