The overall rating reflects the current state of the app. It accounts for all app reviews but prioritizes the most recent ones.
I really want this to work because it does help give site more credibility and you can gauge what product(s) resonates with your visitors. Unfortunately, didn't work well in my shop and support was lacking a bit. I wasn't able to like more than one item in my entire shop. I much prefer the visitors to be able to like whatever product they want, but once they like one item, that's it. I opened a ticket and support wasn't able to resolve it after 1 week (which is the end of the trial period). I removed the app. Maybe it's my theme...but I would definitely use if it worked.