The size in real world units of a single cell is given by the first attribute, with the numbers in the list corresponding to the first dimension, then the second dimension, etc.
The corresponding measurement units for the n dimensions are given by the second attribute.
Regardless of whether the cell shape is a n dimensional rectangle or ellipse, the cell is assumed to fit exactly within the n-dimensional range rectangle defined by cellSize. If the cell shape is a point, then the cellSize is either left nil or is given as a list of zeroes.