Hello people. I have question about battery life. I have iPad Air 2 wifi only. My question is about battery usage. Right now i have about 4 hours and 40mins of usage. And the standby time is 69 hours and 27 minutes. But I have used the device about 3 hours and 30 minutes. So the usage time increased about 1 hour 10 minutes when I did not use the device(device was on standby). Is this normal or is this a problem?