For all battery testing procedure remember to discharge your phone battery until it completely turns off and then plug in your USB meter, keep you phone switched off and charge it, keep it for atleast 3hours after it has been fully charged, then unplug it. If the capacity shown by USB meter is less than 95% of rated 5830mAh, then there is calibration issue with the battery. Repeat this process for 12 to 20 times, generally some good quality cells goes in their peak performance within 10 cycles, I don't know what Samsung had used over here. Remember that after 20 cycles if still battery didn't reached at least 98% of rated capacity, then it might never reach. And after that don't discharge it below 20% and don't charge it over 80%, in this way you can use you battery longer than other. (40% to 70% is best spot, but may not be practical in daily use)
If you are using any app like accubattery after your phone turns off at real 0% plug it in charger, then turn on and put your phone in flight mode, no touching for at least 8 hours, so do it over night for at least 12 to 20 times, but not more than that.
I will share mine result from accubattery once again after a month.
Thank you very much for describing the battery test steps.
It is clear that to carry out the tests it requires lot of time and patience for repeating it over 10 to 20 cycles.
Have a query - "USB Meter" that you have mentioned is name of mobile app or you meant phone power charger along with USB power cable?
Given the time required for doing the battery tests, one has to decide whether to return the phone and ask for a new phone set within the 10 days return policy provided by Amazon or else to wait for battery to stabilize beyond 10 days and then go through Samsung service center to have the battery replaced if it continues to perform far below the number of hours promised in the technical specification sheet.
USB meter is a device that can be used to measure the output from any usb device like current and voltage and hence the other parameters can be calculated. Just search for USB tester in Amazon or Flipkart and watch some youtube reviews.
Remember to read review before buying and before carrying out test turn off fast charging or use normal 10 watt or 5watt adapter for best result.