Nice humidor. I bought my humidor from cuban crafters as well, but it is only a 25 count one. It is supposed to read between 68 - 75 % but 65% is what my humidor is at now and it seems fine.
The sponge, for my humi, is not soaked but wet. I have had the problem that if it compeletly soaked that it causes drips or wet marks on some of my cigars so I don't soak it too much.
As to correct the percentage problem, I suggest to place the hygrometer in a ziplock bag with salt and water in a container to correct it.
If that doesn't work then you should manually change the reading on the hygrometer using the back knob of the hygrometer to around 68 - 75%.