I'd guess that they had already started development before set, because that is insanely early if that's really when they were set. I'm pretty sure any temp high enough to cause such a fast hatch would be high enough to hardboil them too!Nope. Appear to be chickens. Chicken Rancher assured me chickens. From the chart above, 3 are on day 28.
So, assume they were fresh. Assume they hadn't developed before being stuck under the hen. Assume I know what I am doing (big stretch, ain't it Batty?).
Today is 26th - 9th = 17 days under the hen. Still should be 4 days. We have had a high heat and broody stayed on the nest. Good momma.