Spend $50-$99 - Get $10 credit (20% - 10% discount)
Spend $100-$249 - Get $25 credit (25% - 10% discount)
Spend $250+ - Get $50 credit (20% discount and lower)
Funnily enough, it looks like it would be better to make multiple as-close-to $100 orders than one large order as it gives the highest percentage cash back.
T&Cs:
*Limited time only. Purchases must be made between 09:00 (AEDT) 12/2/2019 and 23:59 (AEDT) 26/2/2019 unless extended. Purchases must be made in a single transaction and on eligible products. Shipping charges not included. Credit will be sent to your email address by 22 March 2019. Credit expiry is 6 months. Cancelled orders will not be eligible.
Damn - I bought something a couple of days ago. Looks like I had to settle for 8% off (approx $12 off a $150 item). At least I don't need to shop there again to take advantage of it.