This allows you to add some additional restrictions on the server. 99% of the time , you will probably never use them and they should be left at their defaults. The day of the week setting controls when the server allows connections. You could for instance only allow connections on the weekend. Deny FXP allows you to prevent a user from using your server to transfer files to another FTP server instead of downloading the file directly. Deny reserved ports keeps FTP clients from making your server potentially be used in a FTP attack. Finally the filename filers allows you to control what files are allowed to be uploaded, downloaded or listed in directories. This is where you may want to hide all files starting with a "." (dot).

If you wish to allow only a few items and block everything then use ! in the front of those items, to reverse the logic.