Apple Motion 4 - Manual (Page 691)

If the replicator shape is a rectangle, dragging a corner or edge of its bounding box
changes the Size parameter value. Depending on which handle you drag, you can constrain
the transform to width, height, or depth (in a box-shaped replicator). Or you can drag a
corner handle to scale the replicator in multiple dimensions simultaneously.
Drag the top or bottom
edge to adjust its height.
Drag the left or right
edge of the bounding
box to adjust its width.
691 Chapter 12 Using the Replicator