I suspect they mean 3 through 12, as they list for some other zucchini, not 3 AND 12. I only know this because I looked at that page less than a minute before I read your page and thought, "Hey, that's a lot".
Yeah, that should be 3-12. Love cocozelle, more so than zukes. I grew some in SoCal that got to be the size of a large banana squash. They were still good eating, stuffed & baked.