How much is a cup?
The UK cups are 250mls and US cups are 240mls, so UK half cups are 125mls whereas US half cups are 120mls (quarter cups tend to be the same at 60mls). However, for most recipes, the difference is small and won’t affect the finished dish.
How big is the green Actifry spoon?
Close enough to the 14 ml / 15 ml capacity. You could just use a spoon from your drawer that comes close to 15 ml.