The DN9630 does not contain an ASRC (asynchronous sample rate converter) which means that the the sample rate on the USB side (and seen by the DAW) will match the sample rate on the master (AES50) side.

The toggle switch allows you to specify the overall sample rate, one thing to observe is that the toggle switch sample rate is set at power on, this is to stop the sample rate being accidentally changed during recording.

It is important to remember that you need to unplug the USB cable before changing the sample rate switch for it to have any effect.