Ah, okay thanks. I am also having confusion with school assessment marks. Is it possible to explain how they are marked in relation to your school rank or something? Sorry if these questions sound stupid.
Just to add a bit more certainty, in year 12, there are two types of marks, the average of which is taken to determine your overall HSC mark for a particular subject (i.e. each marks contributes 50% of your overall HSC mark in a subject). They are the Assessment Mark and the Examination Mark.
Your question is relevant to the Assessment Mark. This mark reflects your internal performance. Internal performance refers to your performance in the assessment tasks/exams that you complete at your school except HSC exams. When you complete a school-based assessment task/exam, your mark will indicate your mark in the subject within your cohort. The higher your marks, the higher your ranks are likely to be.
Essentially, if you want to maximise your Assessment Mark in a subject, your goal will be to try and rank as high as possible, which you can only do if you perform at a sufficiently high standard in your internal assessment tasks/exams.
Your rank is one of two elements, the other one being the Examination Mark, that are used in determining your Assessment Mark. This process is called moderation. An Examination Mark is an HSC exam mark, i.e. the mark you achieve in the HSC exam of a subject. The basic rule is that the student who ranks first in a subject will achieve the highest Assessment Mark, which is determined according to the highest Examination Mark achieved in the student's cohort (and vice-versa in the case of the student ranked last).
For example, student A came first internally in Biology. Another student, Student B, achieved 90 as their HSC exam mark, and that turned out to be the highest HSC exam mark in their cohort. This means that not only will Student B receive this mark as their Examination Mark, but student A will also receive 90 as their Assessment Mark, because they placed first internally.
In the case of other ranks (for instance, fourth), the Assessment Mark will not be adjusted to equal the equivalent Examination Mark, although it will be similar. NESA provides the following example:
Notice that the student ranked fourth achieved 59 as their Assessment Mark, although the fourth-highest Examination Mark was 60.
Of course, as dav53521 mentioned, as long as you are doing your best to study/prepare and are performing well, you will be fine.