The VCAA study design for Methods 3/4 at url
https://www.vcaa.vic.edu.au/Documents/vce/mathematics/MathematicsSD-2016.pdf says
*School-assessed Coursework for Unit 3 contributes 17 per cent (with an asterisk because it's moderated)
*School-assessed coursework for Unit 4 contributes 17 per cent.
Exam 1: The examination will contribute 22 per cent
Exam 2: The examination will contribute 44 per cent.
Moderation of unit 3 SAC scores will depend on what a C is at your school and how hard your SACs are relative to the rest of the state. So a high end of year score is still possible at this stage.
My advice is to go over the SAC you just did with your teacher, friends and or tutor and identify your weaknesses and do more practice there. And try and do the same before the next SAC with any practice SACs you can find.
Good luck!