The D/R Ratio (Direct to Reverberant Ratio) display shows the ratio of direct to reverberant sound in dB.

The ratio of direct to reverberant sound is a key factor in determining clarity and intelligibility and is used in many of the EASE simulations, such as the Alcons and RaSTI calculations..
Zero dB indicates the direct and reverberant sound levels are the same, minus dB numbers indicate the reverberant sound level is higher than the direct sound level and plus dB numbers indicate a higher direct sound level.

Notice that in this model, the reverberant sound level is higher than the direct sound level. This is not unusual.