Low fat margarine/spread

Please can someone help with the fat content of low fat margarines? I live in France and can get low fat versions, but I'm not sure how to syn them. For example I can get one brand that is 20% fat and the lowest one is 15% fat.

Can anyone tell me if they have a brand with the same % of fat (15 or 20%) and how many syns that works out at?
Thanks

You can go from the calories which might be easier, as there is no free food its 1 syn for every 20 calories