The overall rating reflects the current state of the app. It accounts for all app reviews but prioritizes the most recent ones.
Although the app is simple to set up, it doesn't really function like Live Chat. Messages aren't instantly sent to your FB inbox. So you could miss messages, which isn't good for business. I was really hoping this would work because of all the good reviews. But it's more like just posting a messenger app on your site. Not like Live Chat.