I'm trying to use WGCNA for weighted network analysis. I'm getting trouble how to decide this parameter. It's clear how to define and why this has been defined.

    #Choosing a soft-threshold to fit a scale-free topology to the network

    powers = c(c(1:10), seq(from = 12, to=20, by=2));

What is the meaning of this powers and how to decide this value? 
In WGCNA,  power parameter is needed to reduce the spurious correlations in the data. To select a power from `pickSoftThreshold` function, choose reasonably high `R^2` (column 2), usually higher than say .85 and negative slope around -1 (column 4) to get an approximately scale-free network. Power is helpful to easily differentiate strong and weak correlations. 