The default ideal temperature for is 12°C.
You can change this from the Cosy App. Enter the settings menu and select "Temperatures". Select the Slumber tab, tap the wheel and adjust the temperature for Slumber. When you're happy, tap the wheel to set the new Slumber temperature.
Slumber mode is the mode to choose for when you want the heating on, but low. Two examples of this would be:
The heating system will always revert back to Slumber when there is not an active heating mode (Comfy or Cosy) in operation. So when a scheduled period of Cosy ends, and there are no more scheduled modes, the heating will return to Slumber until the next scheduled change.
You can put your Cosy system into Slumber mode from the 'now control' screen of the Cosy App, or by pressing the Slumber button on the display. Selecting Slumber will override Comfy or Cosy if they are active at the time.