Now Tested on ten days the data is consistent from one day to the next, for my case about 3000 not an ordinary day at the office (I go by car), 7000-8000 if I add a walking 25 min 13000-14000 and not if I replace walking by jogging 45 minutes. Now I know that on average over the week I am far from recommended 10,000 steps a day.
Very practical also the automatic reset at midnight while keeping the data in memory of the last days = 7> virtually no risk of distorting the data (by combining 2 days) or to lose. In conclusion, I recommend this article for those who have basic needs like mine.