I watched several videos in that regard and during candling you'll be able to see the air cell if there's development. So if there's an air cell it's a keeper. I have a few Barnevelder mixes and that's what I relied on.
I found a thread that goes over the issue if anyone is interested. https://www.backyardchickens.com/threads/eating-infertile-eggs-in-the-incubator.136566/
Heres a question that may sound stupid but here goes.....if you've had the eggs in the incubator for a few days and candle them to see if they are indeed developing. ...I would assume that it's not OK to eat the ones that show no sign of development?
Please add me. I set my eggs today. Spent all day yesterday playing with the heat setting to get it just right. Hope I get a good hatch rate. I didn't candle this batch as I checked some a while back to see if they were getting fertilised. My roosters have been busy so here's hoping. Sadly...