There isn't a default as I'm aware of. Each model has a standard # of procs that can't be changed. That number is typically between 1 and 4 physical processors. Many of these models have multiple core processors as well. I would expect the spec sheets for an individual model to say how many physical processors and how many cores.
I wouldn't sweat too much about the # of procs unless you have a specific issue on an existing config. ONTAP uses procs in a very different way than your standard server so as far as sizing goes, having more procs may help you, but it may not depending on your load, protocols, etc. It's best to work with your local SE to figure out how large of a controller you need.