Ok so I have been using the matrix calculator and these are the marks I used
Eng Adv - 90
Business Studies - 90
Legal Studies - 90
Maths - 90
Maths Ext 1 - 40
Eng Ext 1 - 40
Atar = 88.05
If I remove the two extension subjects and replace them with one 2 unit subject my atar increases...