When iOS displays a grouped notification, a summary message is shown at the bottom of the notification bubble. By default, this message simply informs the user about the number of notifications that are available. You can customize this message by providing a summary format yourself.
Summary formats are tied to notifications through categories. This means that you can add different messages for different notification categories. A custom summary format is supplied in the form of a format string. Update the UNNotificationCategoryIdentifier initialization code in AppDelegate.swift to add a custom summary format for the reminder category as follows:
let summaryFormat = "%u more reminders ...
