The battery does have a cache and software that monitors it. Just like any piece of software there may be bugs, a few percentage points difference between reboots may clear this cache which may make the software to take a new measurement. I should think if it 1-4% at most then should have nothing to worry about.
Unfortunately as phones become more and more technologically advanced then in turn so does the software that drives it. Bugs are inevetable and we as consumers or early adopters such as myself become unwitting beta testers so to speak.
To do a manual check to see how your battery is performing copy and paste this code into the dialer of the call function you will be immediately taken to a new screen. Touch the battery information block to see current status of the battery.
*#*#4636#*#*
Once you are in this new menu I would not suggest changing a single setting unless you are sure you know what you are doing.
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