Niger dwarfs Oceania: about 1,185,111 km² km² against 8,600,000 km² km². At true size Niger is about 7.3× larger — the whole of Oceania fits into Niger roughly 7 times.
The old Mercator map treated both about equally (1.1× vs 1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Niger fits 7× into Oceania.