Because, you have selected Visits.
There will be pages/navigation without Product or Coupen ID (eVar18) while visitor navigates. For those visits, it will be unspecified right? Thus the same.
Ignore the visits and select success events. Conversion Variables should be attributed against the success events and not with base metrics like Page Views, Visits, etc.
To add upon Arun's answer, you will also want to double check your implementation to make sure that the products variable is firing on your order confirmation page. The products variable is not persistent, and therefore must be triggered at the same time a purchase event is set.