This tab has options for how CrushFTP handles its logging. Here you can specify if you want the server to log to disk, and if you want it to keep a rolling log every 10 MB. (you can change this). CrushFTP will automatically name the log files with unique names as they reach the maximum size. You can also control how many lines to put in the server log window.

The other two tabs are the same. One controls what gets logged to the server window while the other controls what gets written to the log file on disk.