Oricon revealed its conditions for the new streaming and combined charts.
For the combined chart it looks like that:
It's based on a point system.
For the singles chart one sold physical copy is 1 point, 2,5 downloads of a single song and 1 download of a full single release get 1 point each, and 300 streams of a song is 1 point as well.
For the album chart one physicial as well as one digital copy sold is 1 point each, while 1,440 streams are 1 point for streaming sites.
The first charts is going to be up in two days.
In the same article Oricon also released statistics of how the current Japanese music market looks like.
Streaming had a bad (and late) start in Japan but within just a year now it overtook digital downloads in total numbers from 2017 to 2018.
It's going to be interesting to see the further developement.