I've not tried this personally, have never been to Westfield Newmarket.
According to the website, the non member rates are $4 per 0.5 hrs
How to unlock this exclusive offer
Not a Westfield Plus member yet? Download the free Westfield Plus App today >
Head to the ‘Parking’ tab in the app and enter your number plate information
That’s it! If your stay is under 3 hours Mon – Fri you will get free parking, plus 2 hours free on weekends