Africa dwarfs Mongolia: about 30,370,000 km² km² against 1,560,428 km² km². At true size Africa is about 19.5× larger — the whole of Mongolia fits into Africa roughly 19 times.
The old Mercator map treated both about equally (1× vs 2.2× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Mongolia fits 19× into Africa.