Wine Cooler Humidity

I purchase a 51 bottle wine built in cooler (Whirlpool) a few weeks ago. Operation so far is excellent (54 degrees nominal). However, when I measure the internal humidity, I get around 30%-40%. I tried a small open container of water in the bottom and rechecked after a a few days but did not see any increase. I don’t know if the meter (temp / humidity) is measuring humidity accurately but I believe I would have still seen a relative increase. Any suggestions on how to increase the humidity (target of 50%-60%) short of misting down the inside of the cooler? Thanks in advance.