About the Australian GPA
Australian universities grade units as High Distinction (HD), Distinction (D), Credit (C), Pass (P) and Fail (F or N). Your GPA is the credit-weighted average of the grade points for those grades.
Most universities, including the Group of Eight, use a 7-point scale (HD = 7 … P = 4); several others use a 4-point scale (HD = 4 … P = 1). Choose your university's scale, then each unit's grade and credit points (often 6, 10 or 12 — see your handbook).