Yeah, way too much information. I can contribute to that by giving "why" to a lot of these things. But the simple answer is lock down after 18 days of incubation.
An egg doesn't have a day's worth of incubation 2 seconds after it goes in the incubator, it takes 24 hours for it to have a day's worth of incubation. So when you start counting the days wait until the day after you start them before you say "1". An easy way to check your counting is that the day of the week you set them is the day of the week the 21 days is up. If they go in the incubator on a Friday the 21 days is up on a Friday. If you count that right then you have counted the 18 days right.
Now for too much information. You do not have to turn the eggs after 14 days of incubation. By then you've gained the advantages of turning. It will not hurt to keep turning them, it's just that you don't have too. Some eggs pip and hatch earlier than others, sometimes quite a bit earlier or later. Part of lockdown is increasing the humidity before the eggs external pip to help avoid shrink-wrapping. Since some eggs can pip or even hatch two days early you up the humidity after 18 days to cover this time of uncertainly. The reason we do everything at the same time is that it is convenient to do both.
To show how critical it is to get perfect timing (not) many people miscount the days and lockdown a full day early. They usually get great hatches too.
I've read that smaller eggs don't take as long as larger eggs. I haven't tried that with bantam eggs but I have checked hatch time on my smaller and larger eggs. No difference.
My eggs tend to pip and hatch two full days early, whether in an incubator or under a broody hen. I blame that on heredity not improper incubation.
I told you I could contribute to too much information. Good luck!
