When I browse 2012 Chevy Cruze, I see my car and my latest fuel-up from this morning. It shows "49.1 Avg MPG" with 4 fuel-ups. However, in the graph above, it shows 2 vehicles with 48mpg and 2 vehicles at 51mpg. Regardless if my vehicle is rounded up or down, there are 0 entries for either 49 or 50. Where is my car shown in the graph?
If you hover over the bars on the graph you'll see a count of vehicles that have a particular average. Right now the minimum threshold for appearing on the 2012 Chevy Cruz graph is 2 vehicles. Which means at least two vehicles need to get a particular average to show up on the graph.
So you just have a particular average that no one else is getting right now, so it's not included in the graph. We can't include all averages once there are enough vehicles—so we group them together like this.