The ordering of OmniGraffle stacks on the canvas

The order of layers in the right-hand column of OmniGraffle influences the stack order displayed on the canvas:

In the first example, the layer order is 1, 2, 3. This puts layer 1 on the top, layer 2 in the middle, and layer 3 on the bottom:

In the second example, the layer order is 3, 2, 1. This puts layer 3 on the top, layer 2 in the middle, and layer 1 on the bottom:

In the last example, the layer order is 1, 3, 2. This puts layer 1 on the top, layer 3 in the middle, and layer 2 on the bottom: