The report categorizes the amount of Leafs you earned and uses your area Nest users averages. So you'll get a Leaf when you choose an energy-efficient temperature.
If you need any more info on the Leaf feature see this page: Learn about the Nest Leaf - Google Nest Help
Hope that helps!
I'd just like to add that I had the exact same question. It's not very clear. If I'm in the top x% in my area, does that mean I'm using the MOST energy on cooling/heating in my area?? That's what it would seem to be. It's worsened by the fact that the middle panel is grey (i.e. bad) whereas the ones next to it are green (i.e. good in this context).
So just to confirm, this means that I'm in the top 25% of area Nest users in terms of efficiency?? As in I'm using less energy than 75% of my neighbors?