Hi @WashR . If you live in New South Wales, Queensland, South Australia, Tasmania or the Australian Capital Territory, your energy retailer is required by government regulations to show you this information on your bill, so it's included on all bills as standard.
These are simply comparisons against the average home in your area, based off data collected by a 2017 survey by the Australian Energy Regulator of 8000 homes. This average would include all-electric homes like yours, as well as mixed-fuel homes. Aside from local area and the number of people in the household, the only other factor taken into account was whether or not the home had a pool or gas heater.
It's just a rough benchmark for comparison purposes, and individual usage will of course vary for all kinds of reasons.
For more information about comparing your energy usage, check out https://www.energymadeeasy.gov.au/article/how-does-your-energy-usage-compare