Oh! I was think that GPA would drop it, but that's good to know it might actually bump it up!!
For anyone interested here's my analysis of UNSW's methodology for combining GPA+ATAR to an equivalent number.
First I believe the statement "high distinctions in some courses and distinctions in the rest" meaning 6.x to maintain 98 ATAR is way too conservative, presumably to allow for students at the HD=80+ unis. I tend to go more with the individual advice of 6.4 UAC/UNSW scale to maintain 99.3 - which is more in line with 7.0=99.9 and 6.0=99.0
Next because ATAR numbers are not linear we need to refer to UAC aggregate table : 99.95=476, 99.0=446, 98.0=430, 97.0=420. It shows the 99.95-99.0 gap is 30 marks, 99-98 is 15, 98-97 is 10. Combining 99.0 with 97.0 would result in a middle point around 98.3 not 98.0, i.e. skewed more toward the higher number.
Thus I estimated 5.75 (around mid-98s) combined with 97.6 should come to low-98s.