gamman and gammat specified in gran model hooke/stiffness

when using gran model hooke/stiffness, I noticed that the gamman and gammat specified are weird for the case of absolute_damping = 'off'.
In another dem code PFC, the parameter specified for viscous damping is damping ratio, however liggghts gives the expression:
gamma(n)=m(eff)*gamma(n,specified)
I wonder if this gamma(n,specified) has a specific meaning that I ignore.

In PFC ,the expression is:
gamma(n)=2sqrt[m(eff)*kn]*gamma(n,specified)
and the gamma(n,specified) is called damping ratio in the normal direction.

thank you.