the rhein ruhr metro and the london metro ( i will not understand) please help !

this are real curious for me, when i take a look on google there are some sites they say london metro counts only 11-13 million and the rhein ruhr counts around 6 million , but there are other sites they say that the london metro counts around 18 million and the rhein ruhr counts around 12-13 million inhabitans , whats really i think that the 6 mllion figures only counts the inner rhein ruhr cites like duisburg - essen - dortmund , Wuppertal , remscheid and recklinghausen and hagen , and the other with 12 million are including cologne , bonn , möchengladbach , aachen stollberg , hamm, wesel , leverkusen . also alo including the famous "rheinland " ;-) ;ok but what is with the stats for i will understand on other hand d there are a big rural area between the southern english coastal cities and greater lon london what counts 18 mil lion : are they including the south english cost with brighton , portsmouth , exeter .. okay than don , this are not the fact by rhein ruhr !? please help whats are realistic with this figures whats are not ???>