My humidor only shows 50, 55, 60, 65% humidity. What can I do?

Are you sure that the hygrometer measures accurately? https://www.german.us/de/content/27-humidor_hygrometer_genauigkeit
The required humidifier capacity depends on the size of the room, the air content, the tightness of the humidor, etc.
In your case the humidor is practically empty and the humidifier capacity is generally not oversized.
If the hygrometer measures correctly, you would probably really need further humidification here:
Important: Have you retracted the humidor? (Wiped out wet, put a bowl of water inside for a few days etc?)
https://www.german.us/de/content/47-humidor-anleitung