With G+, the monthly stats are meaningless since they're probably representative of Gmail logins who accidentally click on +.
I actually did that at least a couple of times last month by mistake, the G+ link is very close to the Inbox/Home link in GMail's web app. I cursed and hit the back button in a matter of seconds each and every time.
Would be interesting to know how much people have accidentally done the same.
And what, we guess that Google is using the Facebook definition? https://www.facebook.com/help/219375581424410/
Which means... unique user page views with 0 engagement metrics! Yay~
MAU and DAU are meaningless statistics. It's pure eye-views, that's all.
Show me some average aggregate visits per user per month, and I'll believe there's actually something happening (ie. the average number of times each unique user visited the site in a single month. Hint: for Facebook, this number is probably ~20-30).