Do you have another unit to compare to, at your precise location? Humidity levels vary wildly, worse than temperature.
Edit: Kudos if every other measurement you have matches, but then , that would also be unusual. For me, the point is not to match others at off locations , it is , to get my measurement as accurate as possible at my location, on whatever I am concerned about. I mean within reason, I mean if you are way off , beyond known device error , etc. 4% on humidity , is actually quite small.