MSRCR

MSRCR Code

Hello Everyone, I need urgent help, I found this code online for MSRCR and I have some parts I really don't understand, Like
b(i,j) =exp(-((i-nn)^2+(j-nn)^2)/(k1*alf))/(k2*pi*alf*10000);
what is this equation about ?
and also why he choose the values of k1, k2,k3 and alfa? its based on what?
I really dont understand, I would be very thankful if someone can able to make it clear for me.
Regards