Incubating 6 duck eggs in an incubator - too few?

[wordgirl]

I've never incubated eggs before, but I'm very excited and want to do it right. I only want a few ducks, so I think I'm only trying to get a few eggs (around 6), but I want to make sure that everything will still go okay if the incubator is not full. I'm Does that affect hatch rate or any temperature or humidity levels?

Thanks!