Nope it says clear as day on their site they track using data compiled from retail outlets or digital outlets.
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MUSIC SALES MEASUREMENT
In addition to monitoring radio airplays, online streaming and music consumer behavior, Nielsen is the authority in tracking what music people are buying both in-store and digitally. Nielsen compiles data from more than 39,000 retail outlets globally, to help record labels, publishers, artists, artist management and performance rights organizations understand what albums, singles and music videos people are buying, and where they’re buying them.

On a weekly basis, Nielsen collects point-of-sale (POS) data in 19 countries across the U.S., Canada, Europe and Oceania. In the U.S. and Canada, physical and digital titles from venues, mass merchants, retail chains, independent record stores and digital download providers can be viewed by UPC, ISRC, artist, market, retailer type or genre.
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SO AGAIN! HOW DID THEY GET #460 IF THEY DIDN'T USE TIDALS NUMBER'S (You know the only digital or retail outlet that had her album available).