Oceania dwarfs Ukraine: about 8,600,000 km² km² against 570,135 km² km². At true size Oceania is about 15.1× larger — the whole of Ukraine fits into Oceania roughly 15 times.
The old Mercator map treated both about equally (1× vs 2.3× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Ukraine fits 15× into Oceania.