That's purely a UQ thing, no other uni uses it. Not sure whether they'd only look at your last 3 years' GPA or the whole 4 years? Maybe give them a call? And it's impossible to tell what the GPA cut-off will be, but I suppose it'll probably be 6+. Griffith Uni dent is not the most popular choice due to the last 2 years of the course being full-fee-paying, but I don't know how much that would drop the cut-off by.