Drop last month's report and this month's — Excel or CSV. You get the cells that moved, the rows that came and went, and the one thing nobody checks for: a formula quietly replaced by a typed number. Insert a row at the top and it still reports only what really changed.
The formula check needs .xlsx — a CSV cannot carry formulas, so on a CSV that finding simply never fires rather than reporting none found.
Your files never leave this tab. They are read here and nothing is sent — compare with your network panel open and watch. The page itself loads one analytics script, which is disclosed rather than hidden: it counts the visit, never the files.