nerge_progression_effect

nerge_progression_effect = {
	save_temporary_scope_as = root_scope
	save_scope_value_as = {
		name = amount_of_players
		value = {
			scope:activity = {
				every_attending_character = {
					limit = {
						OR = {
							is_ai = no
							this = involved_activity.activity_host
						}
					}
					add = 1
				}
			}
			min = 1
		}
	}
	if = {
		limit = {
			OR = {
				is_ai = no
				this = involved_activity.activity_host
			}
		}
		scope:activity ?= {
			if = {
				limit = {
					exists = var:activity_special_type_progression
				}
				change_variable = {
					name = activity_special_type_progression
					add = {
						value = $VALUE$
						multiply = nerge_score_multiplier_value
						divide = scope:amount_of_players
					}
				}
			}
		}
		if = {
			limit = {
				$VALUE$ <= 2
			}
			custom_tooltip = nerge_outcome_boost_tiny
		}
		else_if = {
			limit = {
				$VALUE$ <= 5
			}
			custom_tooltip = nerge_outcome_boost_small
		}
		else_if = {
			limit = {
				$VALUE$ <= 9
			}
			custom_tooltip = nerge_outcome_boost_medium
		}
		else_if = {
			limit = {
				$VALUE$ >= 13
			}
			custom_tooltip = nerge_outcome_boost_large
		}
	}
}

As written in game/common/scripted_effects/00_hunt_effects.txt.