This is the ratio of sensible to total heat in the room for summer or winter.
The total heat gain (summer) or loss (winter) will be determined by adding the Latent and Sensible heat in a room or rooms, i.e.
(SUMMER) Total heat gain = Sensible heat gain + Latent heat gain
(WINTER) Total heat = Sensible heat loss + Latent heat gain
The room ratio is used on a psychrometric chart to determine the supply air state point