If they are muscovy crosses then yes, they'd take 32 days.
However, 96 is very low and 98 is pretty low. The temperatures being that low will cause a late hatch. So it's very possible that these aren't mule ducks, they're just late due to low temperatures.
I would get another thermometer immediately and double check the temp, since the built in displays on the cheaper incubators like this one tend to not be very accurate. Also, does the incubator have a fan in it to circulate the air?
Has the humidity been at 60% for the entire incubation, or...
How high have you been keeping the humidity throughout the incubation? Have you been tracking the air cell growth to make sure it's growing properly? What temperature have you been using? And, have you been using calibrated hygrometers and thermometers to track these two things, or were you just...