The tab lists the file extensions for which ABViewer can be used as a default program.
Associate file extensions with ABViewer: if any extension in the list is checked then all files with this extension will be opened in ABViewer by default.
You may press the Vector Files Only button and as a result only Vector files will be checked. If you press Select All all the extensions will be checked. The button Clear All will uncheck everything.
Go to ABViewer