Sorry but that is in no way accurate. There is no reliable way to measure SOT on IOS devices. Just the fact that I can open an app like facebook and spend a few minutes in the app. Then close it and open another and the screen times are not accurate. I tested it on my iphone 6s+.
I think my iphone 6s+ gets better battery life than my N5 does. But not the 7.7 hours you listed.
Why do you say it is not accurate? Did you do a test? I did. I added the SOT minutes for each app and then added the background times for each app and the time was pretty damn close to the usage time that is listed at the very bottom. Basically: total app SOT+background minutes~usage time. The numbers add up.
What test did you conduct to make you believe that it is not accurate?