You simply press the button and walk away. The chassis, after a short delay, starts to shut down.
You must hold the button down for about 5 seconds waiting for the status LED to turn amber. Do not release it until it turns red. Once it does you can release it and walk away. The chassis will gracefully shut down. If you release it early the chassis will keep running normally.
A simple push and release of the power button initiates a graceful shutdown. If you need to force a shutdown you push the power button and hold it for five seconds. Please note the difference because the procedure to gracefully shut down the SPT-11U chassis will cause a forced shutdown of the SPT-N11U chassis.