Do you have an example? I'm also in the beta, so I can see these estimates as well.
I do know that the estimate is weighted based off your current rating. So if two players played the exact same game, but one is rated 800 and the other is rated 2000, the estimate will be higher for the 2000-rated player.
All that being said, I would take that estimate with a grain of salt. I find the accuracy metrics much more accurate. As a diamond member, you can also use Insights to get even more detailed metrics than what Game Review provides.
Recently I've noticed that after you review a game you played, you can scroll to the bottom and see a rating given to you based on that Single Game. I've noticed that even if I do very well, let's say 89 accuracy or in the 90s, it still rates me low or below average for my range, and when I go analyze higher rated players' games and they've done poorly or have like 4 inaccuracies, 2 blunders and so on, it still rates their single game rating like 2200 or above their average or right around it. Why is this? Is it just going off of the range you're actually in? I just want to know that when I play games and I do very well, that I'm actually doing very well, but I get discouraged when I see this rating very low after a great game..