I have 11 eggs in this type of incubator. Never hatched eggs before. On the instruction sheet it says to fill the center trough for setting and both troughs for hatching. I have been filling the center trough only. Tonight is my lockdown night. When I went to fill troughs with water it looks like there are three troughs. A center one, then one around that one and the one on the outer edge. Do I fill all three? Should I have filled the very center one and the middle one for setting? Confused.