Casual employee: taxed too much on the 1st payslip?

ok so im doing casual work and i calculated that i will get something around $25,000 taxable income this financial year because i will only mostly work 3 days a week, but in my first payslip it says that my annual salary is $41,000 which kinda threw me off.

so anyway, this fortnight i was taxed around 22%, would this be corrected later in my next payslip or would i need to wait to claim this after this financial year?

thank you

When you lodge your tax return at the end of the financial year, your tax payable is worked out according to how much you got paid over the year. Anything that is excess is refunded to you once your tax return is lodged. You cannot get an ad hoc refund of tax from the tax office.
The best thing to do would be to speak to your payroll officer and tell them you believe the $41000 stated as an annual salary is incorrect. Ask them how the figure fo $41000 was reached. Once that is cleared up then discuss the tax you are paying and they should be able to explain it to you and adjust the amount being deducted if needed.

You can claim it anytime you want by going to the tax office.

If you leave it, then at the end of the year, the tax man will realise you've only earned so much and will either give you a lump sum in refund or you'll pay a much lower tax rate next year to make up for it.