The Large Report Filter allows you to set how large the report can be before it will be flagged as a large report. When you run a large report you will be notified and only be shown the first portion of the report. The whole report will be stored and can be viewed in Large Reports. This is done because large reports can take a significant time to run.
To use this filter you check the number of rows you want in a report before it is flagged as a large report. You can also choose if the Large Report option is used. Default settings are Run as Large Report and >5,000 rows.