I estimate Mariah's Christmas digital sales in the USA to be around 4,5-4,7 million copies sold. (+ ringtones 6 million).
The era will def. hit 28,000,000 records sold by mid December and probably reach 28,2 million by year end.
This figure includes 13,400,000 copies sold for Merry Christmas (album) and 11,760,000 copies sold for AIWFCIY (both chartsmasters)