Comfort - the temperature at which a standard woman can expect to sleep comfortably in a relaxed position. If you consider yourself a cold sleeper use this rating to decide the coldest temperature the sleeping bag is suitable for.
Lower Limit - the temperature at which a standard man can sleep for eight hours in a curled position without waking. If you consider yourself a warm sleeper you can use this rating to decide the coldest temperature the sleeping bag is suitable for.
Extreme - this is a survival only rating for a standard woman. Between the lower limit and the extreme rating a strong sensation of cold has to be expected and there is a risk of health damage due to hypothermia. This is an extreme survival rating only, we do not recommend you rely on this rating for general use.