LFG Comp System

Idk how the Comp System in LFG works. When you see the group, you can also see a number next to it. (+/- …) So idk what it means. I’d like to know. My guess is that it’s higher/lower average SR but I wanna make sure. It’s like the green - orange number.
In case nobody knows what I am talking about. Here is an Image:
https ://imgur.com/9nJ8f1C
(I had to make a space between the https and the actual link cuz I can’t provide links in my post)

The +/- 150 means the group requires you to be within 150 SR of its leader