Ah ok, I bet its the same one i have. Im guessing they both have a error of about 10% and are just on opposite ends of the spectrum. It's probably somewhere in the middle (around 60%). If all the other snakes are shedding fine and you don't have wet substrate or lots of condensation on the sides i wouldn't worry about it. You at least know the humidity isn't too LOW, and by checking the things i just said you can ensure its not too high.