I might have a different reference than you- I pulled the manual off their web site a couple of weeks ago. The setup notes in the copy I have state the following:
»INTERN« & »RE-CLK« (Internally referenced Audio re-clocking)
The »INTERN« and »RE-CLK« LEDs will light up when »RE-CLK« mode is selected, indicating that the re-clocking mode based on the internal clock oscillator is now active. As a factory default, »USB-PCM« and »USB-DSD/DoP« are selected as the first available audio reference in the »REFERENCE« menu (the first three LEDs in the column are illuminated). Press the menu key once and you’re entering the »REFERENCE« menu. Toggle the »SELECT« key to select one of the four available audio referen- ces: USB (PCM & DSD/DoP), AES3/11, S/P-DIF op, S/P-DIF bnc. This will now be re-clocked with the internal ultra-low jitter clock signal, format-converted, and passed on to all audio outputs with the same sampling rate simultaneously.
Anyway- sorry I couldn’t help you out more on this but I am interested in these units as I’m thinking about testing it to distribute signals from my playback server to multiple DAC’s. Hoping it would be the right piece for the application.