The fat ratio is a criterion that applies only to fats (butter, margarine and oil) according to the Nutri-Score rating method.
Rather than analyzing the quantity of saturated fat as is the case with other products, it's the quality of the fat that is analyzed, i.e. the ratio of saturated fat to total fat.
The fat ratio is good when the level of saturated fats is low. Although it's very necessary for the optimal functioning of our bodies, saturated fats are today already consumed in excess, which raises the risk of cardio-vascular diseases.