The Document Inspector found one or more active Autofilters or table filters in your workbook. These filters can be the cause of cached or hidden data in your workbook.
For example when you apply a filter to a column, Excel creates a cached copy of the unique values in that column to reflect the current filtering state of the workbook. If you then change that data or remove it from the workbook, the cached copy remains in the workbook until you re-apply the filter.
The Document Inspector can't remove these filter caches for you.
To make sure your workbook doesn't contain unexpected data in filter caches, remove the filters and re-apply them.