If every player of the team is ☆☆★, then 2-3 is the strength of the team, if each player Roll 0.5 stars of the addition (or an average of 0.5), the team strength is 2.5, if all them Roll 0.2 stars, the strength is 2.2~~~~~~ this is my understanding,What I want to ask is,Roll 0.2 0.5 or 0.8 star，which is more probable? What is the probability in terms of a percentage?

Bump...
I would be interesred in the answer to tthis too. I have been assuming it would be an even chance over the gray range. Which would mean that the team in the example above would average out at 2.5.

The bonus is on the skills (balls), the value in stars is only derived from it. If a player can get a maximum of 1 ball bonus the actual bonus in a match is random with chances evenly distributed over the possible range. He'll get the same bonus for all his affected skills in that match, but another player can of course get a different bonus.