And what is the problem? You corrected the reading for one month (e.g. for a value Correction). As result returned values in column 'kWh used' are changed for this month (the change value equals Correction), and for next month (the change value equals -1*Correction).

The total of 'kWh used' remains same (unless you correct entry in 1st or last row of your table), as total change will be Correction - Correction = 0

Another way to look at this: The total is 'Current rdg' from 1.03.2021 minus 'Last rdg' from 29.02.2020, i.e 15175 - 11298 =3877. Whatever happens with values between, doesn't affect this result at all!