Hi,
28 days if you have the Temp set at 100. I'd put them in the hatching tray at 26. Raise the humidity at that time too if you can.
I just hatched about 40+ guineas that I took from a nest after one of the two mommas was taken off the nest by a coyote - I think. Didn't get a real good look at the potlicker.
As things will be, I had chicks hatching the same day as the guineas started to hatch. After having to open the door to the incubator a few times and pull chicks out to toe punch them, I noticed some of the guineas where having a harder time getting out of the shell. I actually had to help several out of the shell before I realized what the problem was. I put the humidifier pad in the water tray and things were fine after that.
Best Wishes with you hatch.
God Bless,