What is the difference between comfort mode and ECO mode for hot water?

In comfort mode, the appliance continuously maintains water at the set temperature, resulting in a shorter wait for hot water but higher gas usage. In ECO mode, the appliance only begins heating water once the hot tap is opened, saving gas but with a slightly longer wait. To set ECO mode, press the eco key until 'eco' appears in the display; press it again to return to comfort mode. (Page 11)