Probably the only person to ask this, but... does this include the portable installments and the e-reader title?
Out of curiosity, I looked up the sales numbers on Wikipedia (lol Wikipedia) and the nine console games combined equal 22.614 million. Mario Party DS sold 8.21 million which would bring the total to a little over 30 million. I could not find sales numbers for Mario Party Advance, Mario Party Island Tour, or the e-Reader game; this would seem to indicate that Mario Party Advance sold under a million, unless its numbers were never reported in a place that Wikipedia could cite. Island Tour may be too new to have a number reported.
So yes, it does include the handheld titles, but not sure about the e-Reader card game. There's a piece missing here to get that 9 extra million. I don't know if they're counting some other obscure stuff that I don't know about, like for example there's some Mario Party sort of arcade game in Japan.