hm, just doesn't make sense to me
84 --> 98 atar, 100-->100 atar
the gap is too big
But you are attempting to scale marks which follow a bell curve to a ranking (the ATAR) which is a flat distribution.
Based on the 2011 stats, 84 scaled to 86.4
Multiply this by 5, and you get an aggregate of 432.
An aggregate of 432 became an ATAR of 98.
At the higher end, 95 in Ext 2 scaled to 95.4
Multiply this by 5, and you get an aggregate of 477.
An aggregate of 477 became an ATAR of 99.95.
Higher than 95 in Ext 2, and you have some slack which will allow you to get 99.95 with poorer results in other subject.
This is what people are talking about when they talk about how well Ext 2 scales.