Why does the one-time discount code show on multiple upcoming orders?
Discount codes are applied on the address profile and will appear on all queued orders under that address. However, if the code is configured to only apply to one charge the code is removed after an applicable charge is processed.
This setup ensures that if changes are made to the order schedule the code is still applied to the next applicable order that processes.
It is recommended to enable the Remove discounts from customer address after discount limit is reached setting to ensure the code is automatically removed once it is used. This also allows a new code to be applied if necessary.