Study scores are altered at the end of the year against exam marks.
As every school sets their own SACs throughout the year, some students will be getting extremely hard SACs whereas others will be getting easier SACs. Because of this VCAA will look at how a school cohort does in the exam and alter the SAC scores to ensure that everyone had an equal opportunity to score well.
Again with the exam, as the study scores are normally distributed, if the exam is hard and nobody gets above a 70% for example (this is probably very unlikely), then the percentage that you needed to be above to get an A+ will be lower.
I don't really know about the 38+ for an A+ in the exam, but my guess would be that it was dependent on his SAC scores, it would be very hard to get around a 38 if you only had D+ on you SACs even if you got A+ in the exam for example.
If you are ranked quite well within your cohort and continue to work really hard. A 40+ is definitely achievable for you. I know that this time of the year can get quite tedious and can feel dry but just keep pushing through it. You are almost there. Try not to worry about marks, just do the best you can.
I wouldn't call myself a study score genius in any way so if anyone reading this thinks that I have made an error feel free to let me know
