The only numerical record is the East India Company series of 1815 to 1828, which covers one presidency, was compiled while prohibition was being argued for, and is concentrated around the seat of the administration that compiled it. The positions in circulation, that the practice was rare and inflated by reformers or that it was widespread and understated, are competing readings of that single series rather than independent measurements. Nobody has produced a count for any earlier period.
What would resolve this A regional demographic study built from evidence the Company never touched: memorial stones for immolated women, which survive in numbers across western and southern India and can in principle be dated, located and counted; vernacular temple, land and family records for periods and districts outside Company reach; and inscriptional corpora already published but never assembled for this question. Both bodies of material have been used locally and never aggregated.
OpenEpigraphy and inscriptional history, historical demography, and regional social history working in the relevant vernaculars.Lata Mani, Contentious Traditions: The Debate on Sati in Colonial India