The NSB stageboxes are no self-standing AVB network devices. It always needs a mixer (console or rack mixer) to control them, which is more a "managing" of network signals (Analog, USB, AVB). Studio One is able to see the complete input section, so when a signal comes in through a NSB stagebox, it is patched to USB and AVB input and output streams and can be routed "anywhere". If you want to record this signal in track 1, just do the appropriate patching and control Gain via Studio One.