That is weird. Originally, the unit itself had that problem - delete a shot and it would recalculate AVG and ES, but not SD. But if you sent the session to the App and deleted your unwanted shots there, it would recalculate everything (including SD) correctly, and this was on an iPhone. Not too long ago they came out with the software update for the unit that crashed everyone's shot detection (v3.30). THEN they came out with another update (v3.32) to fix v3.30, PLUS this included a fix to make the unit recalculate AVG, ES, and SD correctly when shots are deleted. My unit running v3.32 now will recalculate correctly. The App on my iPhone still does, and always has. But while I have updated the unit, I have not updated the App, so it may be that the update for the App that I haven't done yet is where the problem started?