The VRM Box processing takes place at a driver level on your computer. This process incurs a 64 sample latency (about 1ms). The VRM processing also uses a certain amount of CPU resources.
The VRM Box driver will also add additional latency. This latency will depend on how you use the VRM Box:
When using the VRM Box as your audio interface in your DAW, the latency you experience will be dependant on the audio buffer size you set in your DAW, and in most DAWs the actual latency figure is displayed in the preferences. If the audio buffer size is set to less than 64 samples, then the VRM processing does not have enough time to do the processing and no audio will pass. VRM CPU requirements are much higher when the audio buffer size is set too low, so it is recommended that a buffer size of 512 samples (Mac) or 10ms (Windows) should give the best starting point.
When using the S/PDIF input (receiving audio from another audio interface), the latency figure will be dependant on the audio buffer size you set in your DAW for that interface, PLUS additional latency from the VRM Box. In this case, there will be latency incurred from the transfer of S/PDIF audio sent from the VRM Box via USB using the VRM audio driver, through the VRM processing, then back to the VRM Box. The total round trip latency is likely to be in the region of 20ms (depending on computer specs).