DearArvind,

Rain expectation uses the amount of rainfall multiplied by the probability of the rainfall to compare the threshold.

Example: If the smart zone feature is turned on, Netro will skip the schedules when there is a chance of significant rain(>0.2 inch). If rainfall is 0.2 inches but probability is 50%, then 0.2*0.5 = 0.1, 0.1 is less than 0.2, so the watering will go as scheduled. But if rainfall is 0.5 inches with 50% probability, then the Smart Zone will cancel the watering schedule for that day. 

Thanks,

Netro Support