n is the number of leaves used to make up the Spring. You will see that in the theory it is assumed that the ends of each leaf are shaped to a point. You will also see that it is assumed that they all have the same radius of curvature. It is therefore assumed that the leaves could be arranged side by side to give a wide single leafed beam of constant thickness and variable width. ( Of course to do this each leaf would need to be cut longitudinally through the middle, but this is only a detail) The Total width will be n, ( the number of leaves ) times b ( the full width of each leaf.) I hope that explanation helps.