Today, I did 18 flights with four batteries. Three times, the counter of the selected battery was incremented by 1. The other 15 times, the counter of the first battery (which I call the “dummy”) was incremented by 1. I kind of regret this behavior, since I really like the feature very much...
This time the counter was most of the time increased correctly, then I switched to another model and switched back: The increased counters of the previous model were lost. Hope this helps.
Another observation: I used 4 batteries. During the first lap every battery got an increasd counter, the number was displaed correctly. During second lap every battery showed its previous value, in other words the counter was shown reduced by 1.