To add to what Yamster has said, a rank and an ATAR are two different things. Ranks are something QTAC use to compare students with OPs, GPAs and ATARs for the majority of tertiary courses (a rank is on a scale of 1-99 and any student with an ATAR of 99, an OP1 or a GPA of 6.5+ is given the top rank of 99); however, for highly competitive courses like medicine/dentistry/medical imaging which have too many applicants with ATARs of 99+/GPAs above 6.5, a further discriminating factor needs to be used (usually this is just the ATAR or ATAR equivalent to the OP for QLD students). Essentially, many people can have a rank of 99+, but this isn't usually enough for entry into competitive courses, which is why someone with a GPA of 6.5 will likely miss out on a place offer at Griffith dentistry despite having a rank of 99, whereas one with a 6.8+ (also having a rank of 99) is likely to gain a place offer.