Please correct me if I'm wrong, but there is 7.5 syns in 28g of Cadbury choc, and half an Easter egg weighs 55g, so I could have half the egg if I'd used no syns?
As long as thats the caloriies for the egg you've got yes. Basically it's 1 syn per 20 calories so for 15 syns you can have 300 calories, just check the info on the pack to see if thats how many calories are in it.