Look, it's easy if you can count to 7.

Just count up to the fret.

Bottom course open (=0) G
First fret (=1) G#
And so on

Next string similarly

So the unresolved A chord I am using
(second fret on G string, second fret on D string, open A, open E - ie the chord is AEAE) is depicted by the fret number of the note on each string

Hence 2200