Possibly Extinct is a special tag associated with the category Critically Endangered, indicating species that are highly likely to be extinct, but the exhaustive surveys required for classifying the species as Extinct has not yet been completed. A small chance remains that such species may still be rediscovered. See The National Red List.
The database is still under heavy development, several important features are not implemented yet and user interface is not finished. If having some feature request or any other comments, contact developer.