They should be taxing it as per the tax tables, they cannot undertax. You can ask for them to take out additional tax at any time. There is an upwards variation form on the ATO site just for this. Takes less than 5 minutes for them to put the amount in the accounting/payroll system.

The standard rate of PPL is $589.40 per week. The amount tax, if claiming the tax free threshold (what most people do), is $61. So the net payment is $528.40 per week.