Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification".
A cisterna refers to a flattened membrane disk that makes up the Golgi apparatus. A typical Golgi has multiple stacks of anywhere from 3 to 7 cisternae stacked upon each other like dinner plates.The cisternae also carry structural proteins important for their maintenance as flattened membranes and their stacking upon each other.