Battery Reserve confusion or not working?

On the app I have battery reserve set to 10%, but on the battery status display it never goes below 16%.. Why? Is there a 6% safety reserve which it can't go below, in which case what is the point of the battery reserve? Should I set it to 0% or will this damage the battery? Or is there a bug in the app or the firmware?
The percentage on the battery status is naturally expected to show 0 to 100% corresponding to the actually accessible amount of energy, or if 0% corresponds to a completely flat (and damaged!) battery then the graphs should indicate where the actual minimum is. At the top end it does show the battery as being 100% charged when the sun has been shining.

rogerco what's the reserve set to in the portal after you've set it in the app? Sometimes the app isn't great at actually making setting changes stick, the portal is usually better at doing so