Just +1 the badge and add '[modified]' to the title of the notification

notification payload

Connected to APNS
array(1) {
  ["aps"]=>
  array(4) {
    ["alert"]=>
    string(13) "badge testing"
    ["sound"]=>
    string(7) "default"
    ["badge"]=>
    int(98)
    ["mutable-content"]=>
    int(1)
  }
}
Message successfully delivered
119

NotificationService.swift

//
//  NotificationService.swift
//  quickTest
//
//  Created by Christopher Loessl on 2017-07-02.
//  Copyright © 2017. All rights reserved.
//

import UserNotifications

class NotificationService: UNNotificationServiceExtension {

    var contentHandler: ((UNNotificationContent) -> Void)?
    var bestAttemptContent: UNMutableNotificationContent?

    override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
        self.contentHandler = contentHandler
        bestAttemptContent = (request.content.mutableCopy() as? UNMutableNotificationContent)
        
        if let bestAttemptContent = bestAttemptContent {
            // Modify the notification content here...
            bestAttemptContent.title = "\(bestAttemptContent.title) [modified]"
            bestAttemptContent.badge = NSNumber(value: bestAttemptContent.badge!.intValue + 1)
            
            contentHandler(bestAttemptContent)
        }
    }
    
    override func serviceExtensionTimeWillExpire() {
        if let contentHandler = contentHandler, let bestAttemptContent =  bestAttemptContent {
            bestAttemptContent.badge = 42
            contentHandler(bestAttemptContent)
        }
    }

}