Speech transmission index (STI) results

For each receiver the STI component produces 3 results.

I would like to clarify the meaning of these results - do they relate to a subset set of the octave bands like a RApid Speech Transmission Index which I understand analyses only 2 octave bands (500 Hz and 2 kHz) instead of the 8 bands (for which the STI component requires background noise.)

Or have I misunderstood this metric and the three values mean something else?

For reference / a minimal definition I have the open office example (gha and 3dm attached) which includes 20 receivers and the sti results show three values for each (see the image).

Thanks in advance Roly