The window on the right (let's call it Window 2) contains the reset times for an already-existing reminder. (You opened this window by clicking the "Next reset" field of a reminder in the table.)
There is a global option: "Automatic reminders should replace existing reminders (auto refresh)" / "Automatische Erinnerungen sollen bereits bestehende ersetzen (automatische Erneuerung)" If this is disabled, then when the plugin detects quest completion, it will create a new reminder for the quest -- using the reset times and other data specified in Window 1 -- even if a reminder for the quest already exists. Then you will have two reminders; one will be expired, and the other will tell you the time remaining until the next reset.
Normally, people don't want multiple reminders for the same quest. They want the new reminder to replace the expired one. In that case, the "auto refresh" option should be enabled, and all of the information in Window 1 will replace the corresponding fields in the old reminder.
In general, the only time you would need to use Window 2 is for manually-created reminders (created with the "(+)" button). For automatically-updated reminders, it is useful as a quick reference, but there is little reason to change it, because it will be overwritten the next time the quest completes.
There is also a "reset" button (
) for each reminder, which may depend on the reset times defined in Window 2:
If you right-click this button, you can change its behavior:
This window defines what will happen when you click the reminder's "reset" button. If you choose "Defer it until the next scheduled reset time" (Auf die nächste geplante Rücksetzzeit verschieben), then when the "reset" button is clicked, it will get the next reset time from Window 2 and set the current Time for the reminder accordingly.