OK - I am a bit slow to the party here so forgive me if this has already been explained

Just went on to do my entry and can't understand why they have 12'6s doing the marathon!??! Why would you want to do 20kms on a 12'6? Out of 40 odd starters in last December's 20 Beaches I think there were only 2 12'6s?!?!
Anyway - as i am doing the over 40s and open, I have no option but to do the 14s.
Beau, Travis and QLD crew - are you on 14s or a 12s