Hi @Jean-Paul_Durand ,
issues are grouped/distributed in different colors, to better distinguish the issues that receive more recent comments from the ones that receive fewer recent comments.
For example , issues in green have less recent comments and less size refers to less number of votes. Issues in red indicates issues with more recent comments.
Red Issue: Users are deeply involved and they vote and comment
Green Issue: 1 or 2 comments and issues are created long ago.
Please go through below video tutorial , that will be helpful in understanding bubble chart in more detail.
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