What are the pointer boxes containing numbers located on the left side of chord charts?

Hi Igor.

Diminished 7th and augmented are symmetrical chords. The numbers in the box represents the fret numbers, any of which will result in the same chord. In other words, you can move an augmented chord four frets and it will be the same chord, Dim 7 chords repeat every three frets.

Example: The first chord shape for C augmented can be played at the 3rd, 7th or 11th fret.