We test battery life with the inbuilt PC Mark 8 battery test. This continually loops a few day to day computing tasks until the battery reaches around 10% then extrapolates a final battery life figure from that result.
As we've come to expect of machines of this type, battery life is not the GE63's strong suit. You'll got little more than two hours of use, regardless of how low the screen brightness is and how little you're doing.