If you have been refused a visa onshore and you still hold a substantive visa, you might be able to apply sucessfully for a further visa and possibly in due course for a further 485.Basically Grad Visa was rejected due to insufficient study weeks 88 vs a required 92, utter crap and inconsistency in the field.
There obviously is an option for a AAT appeal however the question is, what can I do while on my bridging visa. Am i able to apply to study another course and have the coe issued and roll over? Or do i need to leave and reapply for uni? Coming from tafe and can I work up until my exit date should I choose to go home. Have 30 days to decide
May I suggest that you consult a registered migration agent for advice about strategy?