The homepage has screenshot and a little more information. Below is a description from the script's comments.

// When you visit any page related to a specific Google Custom Search
// Engine, this script displays a small, gray status bar in the
// lower-right corner of your browser. For example, try searching for
// [quinoa] at the Food and Agriculture Organization of the United Nations.
// The result page, linked below, will trigger the status bar:
//
// http://www.fao.org/google_result_en.htm?cx=0181...
//
// This status bar includes this information:
//
// * The search engine's title, which links to the search engine's
// Google-hosted homepage.
// * A search blank -- hit enter to search, there is no button.
// * A "gadget" link: when clicked, you are asked if you would like
// to add the corresponding Custom Search Gadget to your Google
// Personalized Homepage ( http://google.com/ig ).
//
// If you appear to own the search engine, you will also see
//
// * The search engine's statistics in a compact format, linking to
// the engine's statistics page. Format is (day/week/month/overall).
// * A link to the search engine's control panel, context, and your
// annotations.
// * The search engine's unique id. This is purposely not a hyperlink
// (e.g. to the control panel), to enable easy cut-and-paste of the
// unique id. For example, in a typical unix-ish system you can
// double click on the unique id, and it will be automatically copied
// into the windowing system's clipboard.