You seem to be falling into the trap of believing the GOM. It is clearly giving an erroneous estimate. There is no possibility that the capacity of the battery is being reduced instantaneously when you engage guidance. If you feel insecure with the GOM showing rubbish, don't use the guidance, and, when convenient, take the car to the dealer - they need to report the fault to KIA - it is presumably a programming error.
The GOM usually decrements the range estimate by something like 15km when climate is switched on, which is not unreasonable, but there is no logic in such action when guidance is engaged.