How are these numbers calculated?

Big Games

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

Week of 4/24100.0*Chance wins title
Port Vale 2 Notts County 1 -2.6
Hereford 2 Rochdale 1 +1.7
Darlington 0 Notts County 5 Yes
Week of 5/8None
Points
Chance Will Win Championship