Chart Size (% Of Field) property

This is where you specify a percentage to indicate the size of the selected chart object relative to the size of the object in which it is displayed.

The pie chart's shape depends on the size of its field: if the field is a square (height equals width), the pie is a circle. If it is a rectangle (height unequal to width) it is an oval/ellipse.

For bar and line charts, the shape is proportional to the objects in which they are displayed.