Tax on bonus pay versus regular

I work a part-time job, for a small business, scheduled at 20 hours per week at $34/hour.

Occasionally I work 20+ hours a week, but no more than 30 hours, so it’s not “overtime.”

When I work more than 20 hours, the additional pay is listed under “bonus pay” on the paystub. When I asked them why it was considered bonus pay, the office manager said it’s because the payroll software doesn’t let her adjust my hours past 20 hour mark per week, so they just put it as bonus pay.

What do I need to do when I file my taxes? I understand bonus pay is taxed at a different rate than regular pay.