What does "11区" mean?

代指日本。在动画<反叛的鲁鲁修>中，日本被不列颠帝国侵占亡国，成为不列颠帝国的海外领地"第十一区"。

ENRefers to Japan. In the anime <Code Geass>, Japan was invaded and destroyed by the Britannian Empire, becoming the overseas territory of the Britannian Empire, 'Area 11'.