How are these numbers calculated?

Big Games

How we did yesterday and who we should root for today.   Explain

Tuesday, 4/30100.0*Average seed
Severna Park 5 South River 10 -0.6
Arundel 13 Chesapeake 7 +0.1
Friday, 5/3100.0*Average seed
Arundel 7 Severna Park 6 -0.4
Games Above .500
Chance Will Make Playoffs