I have incubated my eggs up to 21 days after being laid and have healthy t happy ducks from this batch
I would set 6 in the bator and on day 5-6 you will know if the eggs are fertile and doing well
Sometimes some don’t take and die in first few days and others don’t ever start. The extra 2 eggs could be replacements if you have any that don’t take or die in early stages
That’s what I would do
Keep them in room temp not a fridge and once or twice a day you can move the two eggs so they aren’t left in same position
Good luck on your hatching

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