The File/Directory Size Monitor is designed to watch an individual file, a set of files, or an individual directory and execute actions (such as notifying you) if it grows too large.
To specify what should be watched, first choose a starting directory. If you are watching remote files/directories, it is important to remember that the monitoring service will most likely not have access to shared drives, so use UNC paths.
Next you select whether a directory, directory with its child sub-directories, or a one or more files should be watched. To watch multiple files, use standard wild cards (ex: *.db for instance).
Last you choose the growth conditions that should trigger the configured actions. They can include growth beyond a pre-set limit, or growth of a certain amount from one scan to the next.

Like all monitors, this monitor has standard buttons on the right for Adding Actions, setting Advanced Monitor Options and setting the Monitor Schedule.