The dosage selector shows which gas mixture the IS-MIX is using.

For the “RED” setting the button must be flush with the retaining ring and for the “GREEN” setting the button should be set to be “deeper” inside the retaining ring and with the pin pointing to the relevant coloured mark. This is to ensure you can check the setting without any vision (darkness). When the IS-MIX is properly pressurised, the button cannot be moved.