Hi and welcome!

I am one that candles around the five day point...lol.
I'll be the odd person out on this one.
On day five you should see the tiny embryo with branches of blood vessels extending from it. It looks very much like a spider. With lighter eggs; white, cream and to some degree light tan...it's very easy to see development within the egg. When you get into eggs from EEs, Marans and Welsummers...that's when it gets interesting. With the darker color eggs, and especially if you're a new hatcher, it's likely best to leave the questionable eggs in until you are certain without a doubt that the egg has died. That may mean the entire incubation period.
The only exception to leaving the eggs in is if you smell a bad egg, or detect oozing/leaking from an egg that's gone bad.
Regarding your egg that appears to have only 1/4 of the chick in it...I'm wondering if what you are seeing is either the air sac in contrast with the rest of the egg or the yolk which takes up a portion of the egg before the embryo has grown and absorbed it.At five days the tiny embryo won't fill 1/4 of the egg.
MC posted a chart showing duck embryo development which take 28 days.
Here are two charts showing the development of chicken embryos during the incubation period.
The first chart shows a clear picture of embryo development on Day 6 which is very close to what you'll be seeing. It shows the air cell at the very top. It also shows the embryo in the top half of the egg and the orange area of yolk in the bottom half. Is this what you might be seeing?
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