Using this option you can exclude the product from this rate or remove this rate from the Shopify shipping.
With exclude rate option you have two options.
i) Remove rate
If you select remove rate then if that product is in the cart or that vendor product is in the cart which is selected on exclude product then system will remove the full rate.
System will not display the rate if you select Remove rate.
ii) Reduce only product price, weight and quantity
This will just remove the exclude price, weight and Qty from the cart calculation. System will send the rate but without collection the information of the exclude product.