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 -0.5
Arundel 13 Chesapeake 7 +0.2
Friday, 5/3100.0*Average seed
Arundel 7 Severna Park 6 -0.7
Northeast 3 Chesapeake 14 -0.2
Games Above .500
Chance Will Make Playoffs