When setting humidity it's best to use the right size containers or sponges of water not mist eggs. Misting is a fast way to spike up humidity but it doesn't last so you're constantly misting and making humidity spike high then low as it dries and you really have no gage what your doing.
If you calibrate a cheapo hygrometer and use that to find what surface area of water is needed in your incubator to achieve the RH you want the easier all this gets. Humidity is related to surface area of water. The depth of water relates to how long you can maintain that humidity, as in it will all evaporate eventually. Misting evaporates immediately and why it's not a good method. A cup holding water is easy to see when you need to add more water. A sponge with wet surface all sides sticking in a cup of water provides a lot of humidity. Play with what works to give the RH you want. Once you know what's needed every hatch thereafter is easy.
Everyones home is different. Some use humidifiers in home and some heat with wood. The ambient (house) humidity is the variable. Dry air into incubator will require more surface area of water in incubator to maintain a certain RH than a home using a humidifier. My house only needs a shot glass to double shot glass of water sitting in incubator to achieve 30-35% RH. For hatch time one of the three troughs in bottom needs water to achieve 70-75% RH. Your house will be different and hence the need for calibrated hygrometer so we all speak the same language.
Salt test:
Milk/juice or some other cap filled with salt.
Add drops of water until saturated, I pour off standing water.
Put cap and hygrometer into a small sealed container, I use a quart size zip seal bag and allow pillow of air.
Wait at least 6 hours, until reading is stable, and record hygrometer reading. A salt environment is 75% RH at all normal home temps.
The math for calibration- Subtact your number from 75 for calibration. Ex. your reading is 84 RH. 75-84= -9 You'd always subtract 9 from your readings for true RH.
