I can't tell you what is right or wrong. What works for me does not work for some other people. We use different eggs in different incubators in different locations. You'll need to experiment a bit and find what works best for you. I suggest you be relatively consistent in what you do so you have a better idea of what you might change next time if you need to change something, or know what to do again if it works. For the first time, I read the instructions that came with the incubator and try that. Then I adjust as necessary.
The idea behind humidity during incubation is that the eggs need to lose a certain amount of moisture during incubation. Some people candle and look at the air sac. There are charts that tell you what it should look like at different stages. Similarly, some people weigh them and get a percentage weight loss at different times. There are charts for that too. Some of us don't worry with candling or weight loss. We just try to replicate what worked before. You can stress about it as much or as little as you want. Your choice. I think it is important to know what you do so you can adjust later hatches if necessary. It's how much you stress about it that can vary.
The humidity requirement changes during lockdown. By the time you get to lockdown, the egg should have lost about what moisture it is going to lose. Chicken eggs are supposed to hatch about 21 days after you start, but often they can be two or even three days early or late. Average incubating temperature is the main cause of that, but other factors can affect it. When the chick pips, the egg membrane can dry out, shrink, and stick to the chick if the humidity is too low. Notice I said it can, not that it absolutely will each and every time. But it can. I know from experience. You want the humidity higher during this time to reduce the chances of this happening. I can't tell you how high it should be. Again, it seems to vary for different ones of us. So again I suggest you try to be fairly consistent in what you do, notice what is going on, and adjust for later hatches.
Good luck!!!
Ya'll seem to know exactly how to do this and what you are doing and I am knew at this soooo there is probably going to be a LOT of questions coming from this direction.
