When clicking on the promotion tab you can see which voucher codes have been consumed by the customer. 

When you can click on the campaign ID you will be guided to the campaign settings which gives you full information on the discount applied.

If you want to add existing voucher codes manually please go to the offer tab and add it directly to the active offer. The code manipulates the price for a specific subscription for a specific length of billing cycles.

Please note

When the time of a discount (e.g. 3 months 50% off) expires the subscription continues and won’t be cancelled automatically.

If you apply a second code to an account for the same subscription while the first one is still active it will overwrite the first code immediately.