Gojs Adornment position offset adjustment

I would like a selection Adornment displayed on the bottom of a node. So I used alignmentFocus: go.Spot.Bottom to achieve my goal. But what I have got is something like this:

The adornment is displayed on the bottom on the node, but inside, then align to the top, is outside.  How can I make the adornment outside?

Here is the solution.

Use the following code instead. This code will offset the Adornment by value of 20 along y axis.

alignmentFocus: new go.Spot(go.Spot.Bottom.x, go.Spot.Bottom.y, 0, 20),

Then I got the adornment position correct.