JSX - my added ellipse is coming in bigger than I set it at

Illustrator stumps me again! Consider the following function. It adds a yellow ellipse 13.5 points down from the center top of the artboard. I expect the ellipse to come in at 10.8pt H and 10.8pt W, but it's coming in at 15.2735 pt X 15.2735 pt. What am I missing? 

var drawBullet = function(layer, doc, yellowSwatch) {
    var abr = doc.artboards[0].artboardRect;
    var top = abr[1] - 13.5;
    var left = abr[0] + ((abr[2] - abr[0])/2) - (10.8/2); 
    var dot = layer.pathItems.ellipse(top, left, 10.8, 10.8, false, false);
    dot.stroked = false;
    dot.filled = true;
    dot.fillColor = yellowSwatch.color; 
};