The tuning error label shows the numerical tuning error in cents. This display is not for tuning. It is for measuring the offset of an existing tuning. It generally is reliable for tuning errors up to 50 cents away from the target pitch. This information might be used for deciding how flat a piano is before you tune it. This field visually updates continuously during tuning, but it is not read out by VoiceOver unless you explicitly select it. When a note stops sounding, the tuning error display will freeze at its last value; this makes it easier to find the field with VoiceOver and have it speak the tuning error amount. But do not wait too long if you want this information. Random room noise, if it sounds musical enough, could cause the captured reading to be replaced by a random value. This can be avoided by touching the field before you stop playing the note you want to measure.