dark spot on egg

Muscovy incubator hatching- first time. Day 36. 8 eggs. 4 external pips and one egg with dark circle on small end of egg?? What is this spot. Does it need help? Also, is external pips large enough? Anything I should do? Lockdown Temp at 98.5 and humidity at 62%. Is this okay? 1 vent fully open...