@syaoran better to secure that slot in Hobart. You can update the test centre and test date later.
Can I change my test location after I have submitted an application?
Yes, if there is a good reason to do so. To change your test location, you will need to log in to myNAATI, select 'My Tests' and follow the prompts.
If you change your test location, you will automatically lose any test places booked at your original test location.
Please note that you will not be guaranteed an earlier test session by changing your test location or language.