Moneybox, I think the reason you are seeing so few targets is that your OzRunways is, by default, only set up to show the aircraft participating in its own (web-based) 'traffic' exchange system. It does not include the ADSB traffic that Flight Radar 24 (and similar) apps display. There is an explanation about how those various systems operate and interact here:
15. Traffic
DOCS.OZRUNWAYS.COM
But there is a way to have ADSB traffic show on your EFB (OzRwys or AvPlan) map page (short of using an ADSB receiver) and that is by using the AvTraffic app. The Premium version allows integration with OzRwys/AvPlan such that it displays ADSB traffic (sourced from the ADSB-Exchange) merged with your own EFB's in-house traffic.
The EFBs use various symbols to indicate the different sources of data. But all of this type of traffic info is subject to some slight delay since it is coming via the internet. For more reliable aircraft-to-aircraft, real-time traffic you'd need to have an ADSB-IN device (like the SkyEcho2 or better).
But even AvTraffic doesn't bother displaying ADSB targets from all over the country (and world) like FR24 etc. because it's designed as a practical piloting tool. Still, I think it shows everything within a hundred nautical miles or more. OzRyws' own system limits itself to the 18 nearest (participating) aircraft, which, at night, might well cover the whole country as your screen shot shows.
AvTraffic
AVTRAFFIC.COM