fix heat for thermal conductivity

Dear Lammps users:
I am using fix heat command to calculate thermal conductivity, and I have some questions about this command.
fix heat command:fix ID group-ID heat N eflux,“N” = add/subtract “heat” every this many timesteps,how much is the“heat”?Is the“heat” equal to the “eflux” in numbers?

Best regards!
NCM.

From the doc page:

Heat addition/subtraction is performed every N timesteps. The eflux parameter can be specified as a numeric constant or as a variable (see below). If it is a numeric constant or equal-style variable which evaluates to a scalar value, then the eflux determines the change in aggregate energy of the entire group of atoms per unit time, e.g. in eV/psec for metal units. In this case it is an “extensive” quantity, meaning its magnitude should be scaled with the number of atoms in the group. Note that since eflux has per-time units (i.e. it is a flux), this means that a larger value of N will add/subtract a larger amount of energy each time the fix is invoked.

Steve