Yes, they calculate those numbers in ideal circumstances, maybe following one of the electric range standards.They advertise 36 miles on a charge, but one wonders if they determined that on a flat test track or in a laboratory. As I have never ever achieved it in the 6-months I've had my Seat Leon eI-Hybrid. When I charge it only occasionally got to '30' miles range, however on day to day driving going up even a modest hill would see the battery drop like a stone. I live 6.5 miles away from work, so a 12-13 mile round journey. In the summer with careful driving I can do this twice (if I'm lucky), however in the winter - it charges less 23-28 miles and if I get to work and back on a charge ten that is about it.
An excellent idea, but the battery range is too low and you do spend your life charging it.
Just like mpgs, those numbers are usually not reachable.