Hi Lucas
That report is a dinosaur from the 1980s and is almost useless. It still exists because of the rule that a developer can never remove a function no matter how obsolete, because there might be one user in the world who would get upset.
If you want a meaningful sales report, you could look under Inquiries | Display History | Items, and select a customer, item and date range. If this isn't adequate, then Adagio SalesAnalysis can do a lot more. And neither of these depend on data that must be purged and therefore lost periodically.
Steve