^You're right. It did sell 10+ million worldwide.
And that was BEFORE digital sales, lol, so basically Utada ROCKS!!!
3 of her albums are in Japan's top-selling albums of all-time.
Those being:
(1)First Love
(3) Distance (I think it's #3?)
and I think Deep River is #10, but again....not too sure.
If Utada had released as much as Ayu during her prime, she probably would have sold even more than Ayu (though I obviously can't say that for certain).
As well all know, however, Utada is not the most frequent releasing artist, lol.