If you do not want to extract all files from an archive you have to specify the names of the files you want to extract.
This can be done in the ``Filename'' field or in the file selection handler. The latter will appear if you click at the button.
Filenames may be given with wildcards. So it is possible to specify *.C as a filename which will lead to extraction of all files with the extension .C. It is not neccessary to specify all of them separately, e. g. FOO.C, BAR.C, ...