Asia dwarfs China: about 44,580,000 km² km² against 9,371,225 km² km². At true size Asia is about 4.8× larger — the whole of China fits into Asia roughly 4 times.
The old Mercator map treated both about equally (1× vs 1.6× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
China fits 4× into Asia.