I don't collect these but that is a fantastic Excel file. Just to help, it does state in that link you posted the following about Atmosphere:
"That move signaled BMG Music's foray into the music library business. In 1994, company president Nick Firth acquired Atmosphere Music, said to be the third ranking company of its type in the U.K., followed by a joint venture it set up with Zomba Music Publishing in Germany in 1995." and continues to say "Killer Tracks is now represented by Atmosphere in the U.K. BMG Music represents Killer Tracks in many other countries, and, as of last January, Killer Tracks represents Atmosphere in the U.S.".
So I think you can mark Atmosphere as being distributed by Killer Tracks in the US.