How are these numbers calculated?

Big Games

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

Week of 4/20100.0*Average seed
Worcester 26 Harlequins 42 -0.2
London Irish 47 London Welsh 28 -0.1
Northampton 47 Sale Sharks 7 +0.1
Week of 5/4100.0*Average seed
London Welsh 33 Worcester 22 -0.6
Sale Sharks 21 London Wasps 20 -0.3
Leicester 32 London Irish 20 +0.1
Games Above .500
Chance Will Make Playoffs