Depending on the brand and size, the configuration will be different. And depending on the brand and type, you can order it how you want it configured. For example, the smaller rotating ovens, you can order any where from 6 to 12 slides.
Just call a bakery oven manufacture like Baxer or call your local bakery equipment supplier and talk to them about your needs. Information is free—and trust me they want to talk to potential customers.