How are these numbers calculated?

Big Games

How we did last week and who we should root for this week.   Explain

Week of 7/27100.0*Home Advantage100.0*Average seed
Canterbury 7 West Auckland 3 -28.0
-0.3
Canterbury 7 Southern 4 -18.2
-0.2
Week of 8/10100.0*Home Advantage100.0*Average seed
Botany 6 West Auckland 2 Yes
+0.4
Botany 5 Southern 1 +28.3
+0.3
West Auckland 4 Southern 6 +0.1
Points
Chance Will Make Playoffs