Reference to picture of mod :

1 = Menace Points per hour = how many Menance point you gain by hours (in-game) when this number reach 100, one horde will spawn

2 & 3 = Minimum and maximum it's number of zombie will spawn each horde

4 & 5 = It's distance from player where zombie will spawn (unit is tile)

6 = Required survival days = How many days your personnage need to be alive before the first horde spawn

For icon you have 4 icon :

Lvl0 = Your are safe for now never horde will spawn (it's when you not have reach "required survival days"

LvL1 = Menance point is > that 0

Lvl 2 = Menance point is > that 50

Lvl 3 = Menance point is > that 75