Currently, the retry schedule is not tied to a regular schedule. The Retry schedule will retry all failed executions from all process schedules. So if the process has more than one schedule defined, the Retry schedule will retry all documents from the failed executions from all schedules.
The attached screenshot shows an example using a very simple outbound process that writes data to a local disk. It is deployed with a regular schedule that runs every 5 minutes and a retry schedule that runs every 1 minute.
In this example, I removed the destination directory on my PC between the 2:45 and 2:50 regular scheduled executions to make the 2:50 regular scheduled execution fail.
Then the retry schedule retried the failed execution at 2:51 and still failed. It shows a red status and shows as a retry by the little green arrow on the schedule icon.
I then restored the directory after this execution at 2:51. The retry schedule retried the failed execution again at 2:52 and succeeded. It shows a green status and also shows as a retry by the little green arrow
on the schedule icon.