I've hatched eggs that were outdoor temps when I found them, in the 30's, nearly frozen, not as high a percentage hatch when they've been that cold but some do. When they're my own eggs and I'm just looking for the next generation I don't much care about probability. I want what hatches from "free" eggs and don't worry about it. I've also hatched previously refridgerated eggs with numbers in the 50-60% range. I've hatched soaked, muddy abandoned eggs - though they needed a LOT of help out because their idiot mother hadn't turned them and they were stuck.
The BEST numbers come from eggs kept in the 55-70 degree range, that are very fresh and normal sized. I like playing with my oddball eggs because every last chick is something I was told couldn't happen or wasn't likely. And I'm like that. So I hatch whatever suits me and much of the time, it works anyway. Nature often finds a way - well outside what "should" work.