blackmesa_mp_coop_gamerules

This entity is not in the FGD by default.
It should not be put directly in a map because it spawns automatically initially..

blackmesa_mp_coop_gamerules is a point entity available in Black Mesa. This entity controls elimination game rules. Spawns automatically with multiplayer game if mp_coop are using 1 value. Spawn via console will result countdown with round restart (without map load), the counters of zombies and waves will not be displayed. If the entity is killed during the countdown, it will partially break the text display. You can use it in combination with point_template when you want to restart round without map load (make sure you removed the previous entity). Since the necessary counters are not displayed after the entity respawns, it is better to restart the round completely by reloading your map.