To add , one of the basic condition to build a stack is , all slots need to have same license level.
This command helps restricting license in the slots to fulfill this condition.
In certain stacking configurations there is sometimes a need to downgrade or equalize license levels among switches so they can be either a master or backup node. This command allows you to set the license level per node or slot to an "effective" license. An example would be if you stacked a X460-G2 to a X670-G2, out of the box a X460-G2 comes with edge and X670 comes with advanced edge. You would either have to buy an advanced edge license for the 460 or issue the command on the 670 "configure stacking license-level edge" (reboot) and you can now have in effect two "edge" licenses to stack a master/backup.