Standard deviation is a variation from mean (average), not median. If you add to your graph a reference line for average, then -1 to 1 St Dev shaded reference band will be perfectly symmetrical in relation to it. Looks like your data is a bit skewed, thus its mean is not the same as median.
And because you used median instead of mean in your table calculations for Windows Max SD and Windows Min SD, you have the same problem with them not matching the edges of of St. Dev. reference band.
Quite right Dimitri,
I had been working on a different dashboard with median and I did not get my calculation right.
Using proper calculation all is correct
Tx for getting me back on track
Your are most welcome.
This "statistics malfunction" stuff happens to me all the time.