The QR code pattern will change every time you look at it, but the information scanned by the QR code will not change. They are all their own health information, such as entry and exit situation, whether they have fever symptoms, etc. Therefore, everyone has a unique digital health code. This string of numbers is different from the QR code and will not change. Just like the mobile phone number, it belongs to personal authentication information. When you go to different public places, you must fill in this string of characters. Everyone's string is different, so don't worry about repetition.