My mum is currently getting 229 out of the Kona with heating turned on and using heated seats/steering wheel calculated at last charge over weekend . I checked what would happen if the heating was turned off and the GOM showed plus 30 miles. I summer when they had the car they were getting a calculated 330-34miles but, they only do local A, B roads and rarely go over the speed limit, as @Stuart points out.
I think EVdatabase is the most accurate where range is concerned.