There is an imac27 in Apple's device list because I recently installed an application on the iPhone by using software like Sideloadly or Aisi. With dual authentication enabled, iCloud will have an additional iMac27-inch record after signing the iPA package with AppleID. Don't worry, when signing the AppleID, you need to simulate a request to log in to the Apple server, apply for a certificate and description file, and you will have a login record after logging in to the Apple server iCloud.