Finger sequencer – plus/minus numbers?!

Apologies if this has already been answered – I did search but couldn’t find anything.

In the finger sequencer, pressing the octave arrows up and down makes +/- numbers appear on either side (up to +4 in green on the right and -4 in red on the left). What on earth does this mean?! It seems to have no effect on the sequence being played or on the various modes (replace, join, fill-in) operate.

Can anyone enlighten me?

it changes the octave for entering notes into the sequencer (shift+keys)

D’oh! So obvious. Thank you!