Europe dwarfs Indonesia: about 10,180,000 km² km² against 1,872,242 km² km². At true size Europe is about 5.4× larger — the whole of Indonesia fits into Europe roughly 5 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.
Indonesia fits 5× into Europe.