How are these numbers calculated?

Big Games

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

Week of 8/6100.0*Chance in playoffs100.0*Home Advantage100.0*Average seed
Southern 4 South Auckland 1 In
+28.7
+0.5
Week of 8/19100.0*Chance in playoffs100.0*Home Advantage100.0*Average seed
Canterbury 5 West Auckland 11 -12.5
-0.1
Canterbury 2 Southern 7 +0.1
Points
Chance Will Make Playoffs