It's what they pay all 21 year old employees. I believe it is the minimum wage plus 25% (loading for casual/part-time, instead of sick leave and annual leave). I do know that it is determined by age - 20 year olds are paid something like 80 cents less an hour, and it goes down to something like 11 dollars an hour for 15 year olds.

Truthfully, I only still have the job because I've been there a while - franchise fast food won't hire a 21 year old except for graveyard shifts - and because I am entering training as a manager. But neither the time I've worked there nor my impending training has changed what I get paid (just my continued opportunity to be paid it).