change_legend_quality_effect

change_legend_quality_effect = {
	# Firstly, do I exist and if not, set me
	if = {
		limit = {
			NOT = { exists = var:legend_quality_progress }
		}
		if = {
			limit = {
				$VALUE$ <= major_legend_quality_decrease
			}
			custom_tooltip = major_legend_quality_decrease_tt
			set_variable = {
				name = legend_quality_progress
				value = $VALUE$
			}
		}
		else_if = {
			limit = {
				$VALUE$ <= medium_legend_quality_decrease
			}
			custom_tooltip = medium_legend_quality_decrease_tt
			set_variable = {
				name = legend_quality_progress
				value = $VALUE$
			}
		}
		else_if = {
			limit = {
				$VALUE$ < 0
			}
			custom_tooltip = minor_legend_quality_decrease_tt
			set_variable = {
				name = legend_quality_progress
				value = $VALUE$
			}
		}
		else_if = {
			limit = {
				$VALUE$ >= major_legend_quality_increase
			}
			custom_tooltip = major_legend_quality_increase_tt
			set_variable = {
				name = legend_quality_progress
				value = $VALUE$
			}
		}
		else_if = {
			limit = {
				$VALUE$ >= medium_legend_quality_increase
			}
			custom_tooltip = medium_legend_quality_increase_tt
			set_variable = {
				name = legend_quality_progress
				value = $VALUE$
			}
		}
		else_if = {
			limit = {
				$VALUE$ > 0
			}
			custom_tooltip = minor_legend_quality_increase_tt
			set_variable = {
				name = legend_quality_progress
				value = $VALUE$
			}
		}
		else = {
			set_variable = {
				name = legend_quality_progress
				value = 0
			}
		}
	}
	# Otherwise, check if the progress is going to go over 100 and if so, cap at 100
	else_if = {
		limit = {
			exists = var:legend_quality_progress
			100 <= {
				value = var:legend_quality_progress
				add = $VALUE$
			}
		}
		custom_tooltip = maximum_legend_quality_discount_reach_tt
		set_variable = {
			name = legend_quality_progress
			value = 100
		}
	}
	# Otherwise, check if the progress is going to go below 0 and if so, cap at 0
	else_if = {
		limit = {
			exists = var:legend_quality_progress
			0 >= {
				value = var:legend_quality_progress
				add = $VALUE$
			}
		}
		custom_tooltip = minimum_legend_quality_discount_reach_tt
		set_variable = {
			name = legend_quality_progress
			value = 0
		}
	}
	# Otherwise, just apply the mathematics
	else = {
		if = {
			limit = {
				$VALUE$ <= major_legend_quality_decrease
			}
			custom_tooltip = major_legend_quality_decrease_tt
			change_variable = {
				name = legend_quality_progress
				add = $VALUE$
			}
		}
		else_if = {
			limit = {
				$VALUE$ <= medium_legend_quality_decrease
			}
			custom_tooltip = medium_legend_quality_decrease_tt

As written in game/common/scripted_effects/06_dlc_ce1_legend_effects.txt.