Microkeeper's PAYG calculation, for Working Holiday Makers will use the annualized wage to deduct the PAYG.
This is a custom calculation that ensures if are expected to earn over $45000 annually they are not undertaxed, and then owe a large tax bill at the end of the Financial Year.
However, it is possible to manually update the tax percentage if the employee prefers the 15% calculation.
This is done in the Tax Details of the Employee Profile, under the Tax Rate Fix Percent area.