This rule set up helps to create a Buy one get one for the same Product.
So when 2 - 3 is added to the cart, only one will be for Free. Same way, 4 products 2 will be for free.
You can provide a discount in the selected Category based BOGO deal.
This is designed as, to provide the cheapest product to be for free. When 2 products of the same category are in the cart then the cheapest product in the cart will be provided as discount.