Humidity reading is 16% when actual humidity is 46%

Recendly, my humidifier had frosted and I concluded that the room temperature was too low. I let it thaw, and decided to take the opportunity to clean the inside. There was a lot of dust on the humidity probe, and I opened the tiny white plastic cage in which the probe rests to make a good job. On the cage, I noticed the number 16 written by hand on it. When I reassembled everything, the humidity readings were way off and still are. I thought that there might be some setting knob to calibrate the humidity probe, but found none.

I certainly did something wrong, but now what can I do to?