Distance to the Moon is about 390 Megameters, time to orbit is 27.32 days, so speed in m/s is:
D*2*pi/T/86400 ~ 1040 m/s
Diameter is about 3500 m, so time of occlusion is:
3500/1040 ~ 3.36
More accurately, diameter ~ 3475m, hence
3475/1040 ~ 3.34.
Seems low to me.