Here are two ways to reduce the statrep.nsf size.

1. Set the Purge Interval (File -> Replication Settings -> Space Savers -> Remove documents not modified in the last X days.) Once the specified interval has passed, run Compact against the database.

2. If you no longer need the data, you can delete the statrep.nsf and a new one will be created when the Lotus® Domino® server is restarted.