Complex sentence: By 1562, the estimated number of Huguenots peaked at approximately two million, concentrated mainly in the southern and central parts of France, compared to approximately sixteen million Catholics during the same period.
Split into simpler sentences: By 1562, the estimated number, concentrated mainly in the southern and central parts of the country. The Huguenots in France likely peaked in number at approximately two million, compared to approximately sixteen million Catholics during the same period.