Re-seasoning a Humi

Another query: I only started re-seasoning my Humi last night, and the reading on my digital metre for humidity inside the Humi was 56/57%.

Out of curiosity, I checked the reading again just now after one night and it has increased to 67% after one night!!! That can't be right surely can it?? The Humi granted has not been opened in about 2 years and there are no cigars in it....there is no way that it has retained the humidity from so long ago surely right? My digital hygrometer must be out of wack lol

Any thoughts??

EDIT: Also I am using a low coffee cup for holding the water, it's small in height so it fits under my shelf in the humi but quite wide so there is a good amount of water in the mug. Could that be a big factor??