Found a full page ad for this in the Daily Telegraph this afternoon while waiting for coffee:
https://imgur.com/a/MU6sqZh
Need to be a new user, submit your email on the site to get a code by Sunday 11:59PM, and then use the credit on Monday (19th), by 4PM.
Seems to be promoting you can purchase food from participating venues now too.
As per Anubis' post below, codes will be sent on Monday, so just a small window of time to use the credit before it expires.
Confirmation page says
Sit tight, eligible registrants will receive a code for $15 credit on Monday 19th November.