What are the 3 red/white combo stones? Why 3?

Set of bamboo plate racks I just got. 8 slots each. I pulled a couple of posts for fat stones.

https://smile.amazon.com/gp/product/B07Z5RKD4J HBlife 4pcs Bamboo Dish Plate Bowl Cup Book Pot Lid Cutting Board Drying Rack Stand Drainer Storage Holder Organizer Kitchen Cabinet (Set of 4) $15.99