Oh, the board computer calculates. Thank god it is a car and not a rocket because those numbers are way off.
When I see 200km left and I'm driving the engine warm and after I trow the AT in "B" from berserk.... just kidding... S or even driving sportiness in D.
Then 40km later I have 40km left.
Other direction is possible as well. Calculated the day before one a small trip, day it self I do a lot of highway but at normal constant speed.
I don't have a ECO button but my foot and mind does it.
Funny was that my distance left was negative one time, it counted -10km.
( 4km trip, starting at 20km left.... )