By default, the coupon code in friend offer is not linked to the advocates who referred friends. Each store’s referral program uses the same coupon code in all friend offers made by all its advocates. 

The following is an exception: If you're using ReferralCandy with either Bigcommerce or Shopify store, each advocate gets a unique multi-use friend offer coupon code that is automatically generated by Shopify and BigCommerce each time a customer is enrolled as an advocate and clicks to send their referral link.  For these stores, each friend offer coupon code is linked to a particular advocate.