Africa dwarfs Australia: about 30,370,000 km² km² against 7,706,009 km² km². At true size Africa is about 3.9× larger — the whole of Australia fits into Africa roughly 3 times.
The old Mercator map treated both about equally (1× vs 1.2× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Australia fits 3× into Africa.