Ok, a few important things to note about our ratings system (especially for OS viewers who might scratch their heads at what might seem small numbers...).
Australia is a relatively small country (population) compared with the UK and the US. Also, the ratings reported in this thread come from OzTam who do not measure the whole population, rather just the 5 main capital city regions.
This link shows a map of the areas covered by OzTam:
http://www.oztam.com.au/documents/other/OzTAM Metro Total TV Coverage Map - Updated 151011.pdf
You will see that the little greeny splotches are are relatively small geographical survey size, however these areas are the largest audiences/population in Australia. So when a show is reported to have a million viewers, it means a million viewers out of those 5 greeny splotches, not out of Australia's ~22ish million.
The population covered by OzTam is 15.8 million individuals which is about 72% of the population.
The rest of Australia is covered by 'Regional Tam' and 'Nielsen Media Research Australia.' Results aren't easily available online for regular punters.
In this thread, the results to be posted here daily are based on live or as live viewing. Which means the program had to be watched by 2am the following morning to be counted (whether live or via PVR).
Consolidated figures come out later (following week) and account for people watching on PVR later than 2am the next day (some time over the following week).
In terms of online viewing; this is from the OzTam website:
What are OzTAM's plans for TV viewing on devices other than the conventional TV?
OzTAM is currently in the implementation phase of metering desktop and laptop PCs (Windows/Mac) as well as television sets within panel homes to capture viewing of TV broadcast-related content. OzTAM is also developing processing systems and options for future reporting. As at July 2013, approximately 15 per cent of OzTAM panel homes had both their in-home TVs and PCs metered. The PC meters capture viewing via the PC of TV broadcast-related content, such as catch-up TV or TV streamed live via an internet connection or a tuner card.
This data comes from within those greeny splotches using a sample population of 3500 homes. These homes are supposed to be a reflection of the whole areas so I am certain that they have a range of different sized homes and I know that multiple televisions within a house are also counted. Apparently even visitors who watch television in a sample home are also counted.
I am just an interested 'ratings-watcher' not a professional by any means, so what I am saying is based on my own interest and research. I could be slightly wrong in my understanding but this is what I have been able to gather.
Note: I am not an OzTam subscriber and do not have a box in my home.