This topic comes up regularly on every ev forum for all makes of car. The suggested range is worked out by the cars computer based on the history of the achieved consumption the algorithms being slightly better or worse in all the various cars on the market. Mercedes are pretty good in my experience.
I am not aware that you can meaningfully reset the system as it will start giving the same stats as you use the car. In essence you can judge your range by looking at your consumption and then compare that to the kw in the battery so 50% SOC equals 40kw which at 21kwh per km gives a range of 190km if you are achieving 20kw/100 the range would be 200 km . The range is a guesstimate based on an average driving history not a fixed level you will achieve. When you charge the car you are putting in energy not a fixed no of km. Search for some of my other posts or other threads on the topic which have discussed this topic at length.
I am not aware that you can meaningfully reset the system as it will start giving the same stats as you use the car. In essence you can judge your range by looking at your consumption and then compare that to the kw in the battery so 50% SOC equals 40kw which at 21kwh per km gives a range of 190km if you are achieving 20kw/100 the range would be 200 km . The range is a guesstimate based on an average driving history not a fixed level you will achieve. When you charge the car you are putting in energy not a fixed no of km. Search for some of my other posts or other threads on the topic which have discussed this topic at length.