Can't change Y sensitivity with First Person Controller?

I can't change the Y sensitivity for the standard First Person Controller prefab. The X sensitivity works fine. I've tried changing the code, (e.g. changing sensitivityY to 1F instead of 15F.) It's always the same speed. (Also, I don't know what the F stands for, if that has anything to do with it.)

Help?

The camera script is on more than one object in the prefab.