First, the term "Multi-million" is ambiguous, unspecific, and questionable. 3 million, 4 million, 32 million, and so on are also "multi-million". You can not just assume "multi-million" = "2,000,000", that's simply WP:OR. We really need a source writing explicitly 2 million copies. I wonder why her label did not write the exact number for Memoirs sales, while at the same occasion they wrote 12 million for Merry Christmas and 10 million for TEOM? 

 Second, don't forget that the album is a commercial disapointment. It only received Gold in USA (500,000), and its overseas sales centainly would not the triple number of it, conridering only Silver in UK, gold in Brazil, and acccording to Carey's website Platinum in Korea. Not to mention, the album is uncertified in world's largest market like Japan, Germany, France, and Australia. Surely, I believe Memoirs sales are not higher than One million, based on its chart performance and certifications.