Always-on or Standby Power is defined as the lowest power measured within the last 2 days. This is the consumption of appliances that are never switched off. Think about a TV, Internet modem/router. Add a Smappee Switch or Comfort plug to automatically switch them off when you don't need them to save energy.
If the monitor has been recently installed/re-installed, reconfigured or powered off, it is possible that the always-on value will not be displayed. The always-on value should be visible after about 2 days.
The always-on is also displayed on the main page of the App, just below the bubbles.