is it accurate? My zoo med is 27% low... the test is easy. Paper is hydroscopic and draws moisture out of the air and becomes damp. Tear a bit off and see if it feels damp if it does it is likely a bit too high if it doesn't again likely it isn't.

salt test link...

http://cigars.about.com/od/humidors/qt/hygrometers.htm

if it is out you'll have to just do the figuring it cannot be adjusted.