Oceania dwarfs South Sudan: about 8,600,000 km² km² against 623,998 km² km². At true size Oceania is about 13.8× larger — the whole of South Sudan fits into Oceania roughly 13 times.
The old Mercator map treated both about equally (1× vs 1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
South Sudan fits 13× into Oceania.