On the player count card, there is a big number (white in a black circle) on the lower half. Does it have any use for the game? I only played The Goblin Problem scenario...

Thanks in advance

That is how much extra maximum health each hero starts with. In a 2-hero game, each hero starts with 10 extramaximun health; in a 3-hero game, each hero starts with 4 extra maximum health.