I using a water bottle with tubing to add water to the incubator without lifting the lid when the humidity level drops below 27%. The lines on the bottle equal 1/4 cup of water and when I add 1/4 cup of room temperature water the humidity raises to 60% for a couple of hours and the drops down into the 40's for the remainder of the day. A few days have required an additional 1/4 cup after dropping to 8% when the water channels are completely dry.
The humidity alarm is set at 45% when you purchase your Janoel8 and you'll need to lower the humidity alarm settings if your goal is to have a 30-45% humidity level through day 18. Their are some good articles reference Dry Hatch Incubation on the web.
When day 19-21 rolls around the water bottle will work nicely and one won't have to lift the lid to add water. This should improve the hatch.