For most situations, this can be left off. But for extremely quiet weapons, the buzzer may be louder than the gunshot so it is necessary for the KST1000 to selectively mute during the buzzer. This means that it will not detect gunshots that happen concurrently with the start beep, which is defaulted to 300 ms. While scrolling through this setting, there are also plus values. These are essentially echo values for the buzzer mute.