What is the meaning of SMS ringtone fadeln in Xiaomi system?

The ringtones used in different versions have changed. Recently, the miui system has been updated to the latest miui7, which will add default themes, including boys' version, girls' version, goddess version, deluxe version and default version. Moreover, the system ringtone has also been optimized, replacing the less used ringtones before. Your updated version may have replaced the ringtone. It should not affect the use.