Is there detailed information about what counts as a Google+ MAU? It's not totally clear what they are counting and how much of them are true MAUs of the socia

Is there detailed information about what counts as a Google+ MAU? It's not totally clear what they are counting and how much of them are true MAUs of the social network versus people who have Google accounts who somehow interacted with something Google+ related while signed into Gmail (e.g. accidentally clicked on a +1 next to a search result, or the notifications in the black bar). I'm a Google+ MAU, since I'm usually signed into my Google account, and occasionally read blog posts on Google+. I'm a Google+ MAU in the same way as I'm a MAU of plenty of other blog hosting sites. I don't use it as a social network. I think more detailed engagement numbers would tell the true story.