You need to work out for each unit you did what your result was /100 and assign it a high distinction (for my uni this was scores 80 and above), distinction (scores 70 to 79), credit (60 to 69), or pass (50 to 59) rating.
Then convert the word grade to a GPA grade
HD: 7
DN: 6
CR: 5
PP: 4
Then add them up, then divide by total number of units. That gives you your GPA on a 7 point scale. Then use the guide based on the FTE you’ve done and see if there’s still a discrepancy.
Keep in mind, FTE at most Aus unis is 8 units.
As per the table: you’d need 6.5+ on a 7 point scale to get a selection rank 99+ for UQ.