Tree Creator Frequency Value cannot be set

I need some tree models for my game I've been creating and so I thought I would build them with Unity's tree creator. Well I was following the tutorial posted in the wiki and I've hit a problem pretty early on. I'm supposed to set the frequency of the branch node that I added and for some reason I cant set any value in the frequency field. Frequency is currently set to 1 and I can delete that but I can't set any other values. Anyone have an idea of what's going on here?