I think those stats reflect completely different things. The stock one is over a 10 hours period and Gsam just a little bit more than one. My guess is that you partially charged your phone and the stock stats are from the last full charge and Gsam just since the phone was unplugged. It's just a guess from that little info, tell me what you think.
Edit. Tap on the battery graph and post the screenshot. That will tell if there was a partial charge included in the stock stats.