Its hard to say because it might have been downloading updates or doing something else in the background. But i think its fairly normal. Apps like gmail and news apps keep refreshing in the background in order to give you notifications about important things so even in standby it will drain faster then you might think
That’s almost the max and will take a lot of power. Reduce if you can. Adaptive brightness is useful particularly outdoors but will tend to push brightness up beyond what you really need in my experience.