It depends a lot on total climb, your weight, and how much effort you put in (rather than letting the motor do it). It has a pretty small 200wh battery, so 5 miles for 50% is not that improbable.
That sounds about right. If you have a typical 15 amp controller, that would drain the battery at up to 600W and last about 20 minutes. A 5 mile hill at 10 mph is going to take 30 minutes, so you did pretty well to have half you battery left.