As I say every year...
The HSC timetable is designed purely based on that years cohort and the subjects they are undertaking - i.e what works best for the majority of 2008ers (basically trying to ensure the least number of people have 2 exams at one time).
Actually they do put exams on the 'same time slot' when there are students who do those 2 courses. This is because usually there is no possible combination that allows for everyone to only have one exam 'at a time' (unless they extended the exam period obviously). So the aim is to minimise the number of students who have 2 exams at one time.
Also, it isn't necessary to pick up every minor spelling mistake on the forum. It's an internet forum, we don't judge people based on their spelling mistakes/typing errors etc. Everyone isn't perfect and there isn't really a need to be - focus on the 'big picture'.