the sun - Calculating effective SSN (sunspot number)

I am doing research on SSN like parameters. As I can see effective SSN is a parameter that derived from SSN or may be using other parameters. Do anyone know how to calculate effective SSN.

i.e following file has some parameters ftp://ftp.swpc.noaa.gov/pub/latest/DSD.txt

ref http://spawx.nwra.com/spawx/ssne.html

Thanks