Why do some products randomly generate OPC variants in my online store?

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Hello, I am wondering if anyone knows why some of my stores products will randomly generate a variant starting with the letters OPC followed by a random set of numbers. I will add a photo of my Shopify admin product view so you can see what I am talking about. On some products, I will have one of these random OPC variants and then on others there will be 10-15. None of the products on my webpage have tracked inventory, but these variants all include a random amount of inventory with them that says we have in stock. However, these variants are not viewable by the customer, only on the admin view... If anyone can tell me what these are, how to get rid of them and prevent them from recurring or what they mean that would be great.