Pack Size is (-1) - (0)

https://ibb.co/VNL7tKQ https://ibb.co/8Pq4pHz

I don't know how to format this correctly but as you can see in the screenshots, there is a bug that shows the amount of monsters in the pack as -1 to 0 Monsters. I assume these monsterpacks aren't supposed to spawn but still show up in the overview on the Lantern of Arimor

Edit: Additional Info it's Lair of the Hydra map with "Area is inhabited by skeletons" modifier.