Yes, it's the total playcount, if you use Spotify on a PC you can check it, the songs that share the same tittle share the same ammount of plays, SEASONS (single, duty, a best, a summer best, etc) all of them have 6M (almost 7M) streams in total, but every version of the same song with a different tittle (SEASONS - So Happy So Sad remix, SEASONS A Classical Version, SEASONS live from PoM 11, etc) have their own total playcount
The next songs to reach the 1M mark are:
progress 989,544K
glitter 984,500k
Love song 979,612k
aeternal 977,316k
I'm so happy for aeternal being kinda popular lol