Given this information, I believe that you could be looking at an ATAR no lower than 98 and up to 99.95. Your performance is evidently favourable across your subjects and is highly likely to make a substantial contribution to your ATAR. It is therefore important to continue to prepare thoroughly for your Mathematics Extension 1, Mathematics Extension 2, Physics and Software Design and Development HSC exams (best of luck!
) in order to ensure the best possible performance, which will in turn hopefully maximise your chances of achieving your ATAR goal.
Despite your favourable position, the only subject that could potentially limit your ATAR potential slightly is English Advanced, although this should not be substantial because it is still a high standard of performance. Hopefully, you would have done well in your English Advanced HSC exam, allowing you to maximise your HSC mark in this subject, ultimately increasing your chances of reaching your desired ATAR even further.
I hope this helps!