Port 6 is an Always On DC output, which is suitable for equipment that needs to be powered on all the time such as your computor.
Ports 4 and 5 are PWM outputs , which allow mannual or auto control of your dew heaters.
Ports 1-3 are three DC outputs connected in parallel .They can be turned on or off at the same time, suitable for power supply for your CCDs , rotators , focusers , etc .