I have a question about designing custom shapes for nodes.

I've attached an image that should appear at the bottom of this post. The image demonstrates that shape I am attempting to achieve, and what I have been able to get so far with my code.

Here is my code for my custom node:

public class AddNode : MindFusion.Diagramming.ShapeNode
{
    public AddNode(Diagram parent_diagram) : base(parent_diagram)
    {
        AnchorPoint input_x = new AnchorPoint(0, 33, true, false);
        AnchorPoint input_y = new AnchorPoint(0, 66, true, false);
        AnchorPoint output = new AnchorPoint(100, 50, false, true);

        AnchorPattern = new AnchorPattern()
        {
            Points = new AnchorPointCollection()
            {
                input_x,
                input_y,
                output
            }
        };

        Shape = new Shape(

            new MindFusion.Diagramming.ElementTemplate[]
            {
                new LineTemplate(0, 0, 0, 100),
                new LineTemplate(0, 100, 100, 50),
                new LineTemplate(100, 50, 0, 0)
            },

            FillMode.Winding

        );
    }
}
 

This code creates a triangle that is too elongated in the horizontal direction. If I replace the shape code with this:

Shape = new Shape(

    new MindFusion.Diagramming.ElementTemplate[]
    {
        new LineTemplate(0, 0, 0, 100),
        new LineTemplate(0, 100, 75, 50),
        new LineTemplate(75, 50, 0, 0)
    },

    FillMode.Winding

);
 

Then the triangle is about the right shape, but the AnchorPoint is offset.

What are the units being used here? Why does "100" in the vertical direction equate to 3 grid boxes on the diagram, whereas "100" in the horizontal direction equates to 4 grid boxes on the diagram?

For what it's worth, on my diagram I set GridSizeX and GridSizeY to both be 10, if that is important.