I've read everything I can find on humidity at lockdown and there is a lot of confusion. This is my first hatch, so I'm trying to get it "right" as much as possible.
The various things I've read have been:
--60 is fine, just don't open the incubator.
I've also heard heart breaking tales of overly wet, drowned chicks because the humidity was too high, and shrink-wrapped chicks because the humidity was too low. I feel like I'm threading a needle!
I'm using the Brinsea Oct. Advance 20. Day 1 thru 18 my humidity ranged from 40-45. I've now read about the many successes people have had with "dry-hatching" and fear that this may have been too high. The instructions with the incubator were to set it between 40 and 50, so that's what I did. Nothing I can do about this now.
At the start of day 18 (last night), I filled both water trays and the humidity stabilized around 57%. This morning I then added a damp sponge and it is now at 62. I'm reluctant to keep opening things up to fiddle with humidity. One part of me says to walk away, that low 60s is good enough, the other part worries that I need to keep fiddling to raise the RH. I've heard or seen no signs of movement yet, so I still have a window to go back in.
I also failed to weigh them or mark changes in air-sac size, as a feared over-handling the eggs. Probably a mistake in retrospect.