The object of isolation is to stop the spread of Covid-19 in the community. But how many of the cases detected in a day should have been in isolation?
Community case to community case spread will slow and stop when community to community effR is 1 (or less). And it is possible to calculate the number of cases that would occur in the community if the effR was 1. All the rest of the day's new cases should have been in isolation. If they were, then the current wave will end, if not the current wave will continue.
Plotting the number of cases that were isolated and the number of cases that should have been isolated shows that each day Australia is far from isolating the necessary number of infected cases.
The effR of community to community spread is probably showing a slight downtrend, but contact tracing with Delta strain Covid-19 has not managed to isolate the necessary number of cases.