Actually, I believe the reported average consumption is fairly accurate, but the reported battery percentage is very inaccurate. We already now that the reported percentage (we like to call it SOC) is not linear. If you charge the car and let the battery have time to balance properly, you will notice that you can drive fairly long before the SOC goes down to 99%. Also, there are reports saying you have a similar situation when you reach 0%.
I think we can assume around 3kWh between 100-99 % and the same from 0%-stop. That's leave only around 79 kWh for the remaining 99%-0%.
In addition, it looks like the SOC is not linear in the interval 99-0% either, so any calculation involving a small SOC interval is doomed to be flawed.
If you charge the car completely full and run the battery all the way to 0% is displayed you can calculate the used kWh my multiplying the average consumption with the distance. Add the last 3kWh from 0%-stop and I think we will
be fairly close to the claimed 84.7kWh. At least if you do this when the ambient temperature is not too far away from around 70 degree Fahrenheti (20 degree Celcius).