I'm thinking that the number of holes is related to the number of eggs the incubator holds. I've tried to read about this , and my LG isn't the same model as yours, yet I keep reading about the need to increase the number of holes at day 10 for chickens (day 14 turkeys) to increase the ventilation ie oxygen. Apparently the bigger the chick grows the more gas exchange takes place thru the shell. The chick will need more and more oxygen, and to get rid off carbon dioxide and other gases.
Here's a thought.Did you know that mammals inhale to breathe based on the build up of carbon dioxide; our breathing system is not oxygen based. We need oxygen, yes, but the triggers in our body to breath is based on an increase of carbon dioxide, not a decrease of oxygen. Perhaps, just perhaps, the bird is designed the same way. I'm not sure where I'm going with this idea . . . .Maybe I just mean that the eggs need more gas exchange and ventilation at an earlier day in the incubation(day 10), and another increase again at day 18, hatch.
FYI:I've only been reading alot; still on my first attempt to hatch.
Good luck
LG : 40 eggs, 8 holes top, 8 holes bottom AND 2 large holes, about 1/2 inch diameter tat can be closed (or opened).