Battery question

I got my buds today. My buds 2 pro fit better in all honestly but maybe I'm still getting used to them. Controls are very different and by that I mean there is no feedback so if I pause or increase/decrease volume, or change songs, nothing. They action happens but I was used to the feedback from the 2 Pro. Anyway my question is about this picture, there are 2 dots underneath the battery percentage, and no matter what I do only the right one is darker grey, anybody knows what that means? Both buds work