[gmx-users] g_lie question

[EGY]

I am trying to figure out how to use the g_lie tool in gromacs. I have the dGbind value for the ligand-solvent interactions and for the protein-ligand complex.
However, I cannot find in the manual what units these values are. I get the following:
DGbind = 1953867.080 (0.664)
and 
DGbind = 185147.449 (nan)

What does the parentheses mean and what is (nan)? And, what units are these in?

Any input would be greatly appreciated.
Thanks!
2egy