New Customer Discount

I would like to create a discount which has a use of one time per customer, applied automatically when order exceeds 1$. This is possible in the options provided when creating a discount.

However, I am unsure of how Snipcart keeps track of customers.

I understand the difference between a confirmed and an unconfirmed customer being one who does or does not have a customer account through Snipcart, however I have also noticed that Snipcart will keep track of how many orders have been placed by the same unconfirmed customer.

Thus, it should be possible to create this discount for a customer to use once on their first time order.

However, if the customer checkout is set as guest checkout only, would each checkout still be counted as a new customer, or would a returning customer with the same billing and shipping data be considered an existing customer?