On the day Reminder Notifications are set up to go out, a notification will be sent each time the form settings are saved, regardless of whether or not any changes were made.
For example, my form is due on 5/30 and the Reminder Notification is set to "7 Days before the Due Date". Reminder Notifications will be sent on 5/23 for this form. So any time the form Settings are opened and saved on 5/23, a reminder notification will be sent, regardless of whether or not a change was actually made to the form. If I open and save the form settings three times, I'll trigger three notifications. On any day other than 5/23, the form Settings can be saved without triggering additional notifications.
If using the "Send when activated" reminder option, a notification will be sent each time the form Settings are saved on any date if the form is Active.
On the day Reminder Notifications are being sent (or on any day if using the "Send when activated" option), if you need to open your form Settings but do not need to make any changes, you can use the "X" or Cancel options to close the form Settings without triggering a notification.
If you need to save changes to your form on the day Reminder Notifications were sent, but you do not wish to trigger additional Reminder Notifications, make the Reminder Notification Inactive before saving your changes. (If you re-activate the Reminder Notification, saving will trigger a notification if the option is still set to send reminders today.)