C3 is middle C in Logic's piano roll view. I assume it's the same in Garageband(?)
You could always draw a C3 note in piano roll view and then switch to notation view and see if the note is between the two staffs.
Because you learn middle C is C3 if you study music as an art.
Although the
scientific pitch notation system uses middle C = C4, within the world of
Western music middle C = C3.
To further confuse the issue, because the
MIDI standard does not specify a particular octave numbering, different types of MIDI keyboards by different manufacturers may label either C4, C5, or C3 as middle C (note 60).