An outside source: "SGI has only 40,000 - 100,000 members worldwide"

In addition to money and buildings, Soka has its own built-in applicant pool. Its founding institution, Soka Gakkai International (SGI), is a lay affiliate of the largest Buddhist sect in Japan, estimated to have somewhere between 40,000 and 100,000 members worldwide. - from 2002

I got their "12 million" RIGHT HERE O_O