(please add your followups as comments not as new answers)
the 20 is the smoothing factor (gaussian kernel width), think of it as the window over which the averaging takes place. The smaller the window the more sensitive the method but it also uses less data to average. A window of 20 for a feature that spans over 140bp is fine in general The Galaxy version as I said is not supported in any way so I can't comment what it produces or even why. I can't access the code that runs it.