makeCloud question

Hi

I am reading the link below for makecloud function and have some questions

https://yade-dem.org/doc/yade.pack.html?highlight=sp%20makecloud#yade._packSpheres.SpherePack.makeCloud

1- why the "rMean" and "num" are negative? as I know rMean is the mean value of particle radii and num is the number of particles in the packing. So, I think rMean should be something like 0.2 mm and num should be something around 1000 for example.

2- the way these variables are used in makecloud function is to just put them in order and separate them by " , " ? I mean it is not possible to define: porosity = 0.4 ? I tried it in this way and got an error.

Thank you,
bests