I didn't know Asda had 30% less fat sausages (I can't see them on the ASDA website either). Are you sure they're not the 50% less fat ones - these are 1 syn each on Red and EE, and 4.5 syns on Green.
If you post the nutritional info (per 100g - fat, calories, carbs and protein, and the weight of the whole pack) we can get a value from the syn calculator for you.