Okay someone who knows tax help meeeeee. I just got my first payslip, and ive just been taxed $78

I work casually, I only earned $120. and got taxed more than half my pay? Idk this doesnt seem right. I am going to ask my supervisor at work, but just wanted to ask if anyone may know why.
Also the pay slip says 'please give tax number asap' when I did actually give it to them. So idk