From this panel you can choose to write your own custom appended file extension to your patch files to be uploaded to your webserver.
The default is gppc.
The Reason for Custom Extensions
You maybe distributing your game to a handful of players or millions of players worldwide. Lots of users have antivirus products installed, firewalls, external firewalls and much more. Sometimes, if a process (or patcher) tries to download some files like executable (exe) or dynamic link libraries (dll) a third-party app might break the download or attempt to stop it.
To get around this, we append a custom extension to the end of each of your game files. This is all done automatically, so you don’t have to do anything yourself.
Some webservers also don’t like exe or dll files being downloaded or even read, so we have to append all files to be patched with a custom extension which breaks this mould.