The menu does only show one meal but there are about four different main course options on there, and the menu seems to imply that you can have either one or two meals depending on how hungry you are. The exact quote from the menu is "Whether you would like your meal to be served soon after take-off, or two hours before arrival or both, simply inform our crew and leave the rest to our care."

In practice, there will actually be two rounds of meal services on that flight - one right after departure for passengers who choose to eat then, and another for those who choose to go to bed after departure and have breakfast before landing in Sydney.