Modern versions of excel (after office 2007), using .xlsx files, have a 1,048,576 row limit. But older versions of excel (before office 2007) used .xls files and had a limit of 65,536 rows.
I could easily see them exceeding this limit, if they were using an older version of excel.
Alternatively, even the new versions of excel enforce the 2^16 row limit if working on a .xls file instead of a .xlsx file.
I could easily see them exceeding this limit, if they were using an older version of excel.
Alternatively, even the new versions of excel enforce the 2^16 row limit if working on a .xls file instead of a .xlsx file.