It's a difficult thing to decide on really. You can get some with only 7 chapters, but each is 80 odd pages long, giving it a total length that's more than some with 50+ chapters. Then you've got additional complications like filler pages (a lot have a few pages of character designs etc) credit pages and such. All of that pretty much rules out any automated process, and then you're down to whether one person considers it short. This is of course without then debating where the line is drawn, is a 9 page per chapter considered short? Does that mean 10 is long? There's just too many variables really, and not enough reason to do it for it to be worth it, in my view.