Spekle filter parameters seting of S1-GRD data

holle everyone, I want to do the speckle filter for S1-GRD data, in this process, I would like to choose the Gamma Map, but in the parameter setting of number of looks, I have no idear, what should I do? althouth I know that, data that I downloaded has been multi-looked, I didn’t how to set the parameters.
thanks a lot