why then font use tocanvas.TextOut is very small?

in the demo 《Annotation》，in the function of Paint to Draw text,i find the text is very small,why?

procedure TWPOAnnotation.Paint(toCanvas : TCanvas; BoundCanvas : TRect;
ParentTxtObj: TWPTextObj; PaintMode: TWPTextObjectPaintModes);
var x: Integer;
begin
//! OBSOLETE UpdateBoundCanvas;

toCanvas.Brush.Color := clWhite;
toCanvas.Brush.Style := bsSolid;
toCanvas.Pen.Color := clRed;
toCanvas.Pen.Width := 2;
toCanvas.Rectangle(
BoundCanvas.Left,
BoundCanvas.Top,
BoundCanvas.Right,
BoundCanvas.Bottom);
x := (BoundCanvas.Left + BoundCanvas.Right) div 2;
toCanvas.MoveTo(x, BoundCanvas.Top + 2);
toCanvas.LineTo(X+10,BoundCanvas.Bottom - 7);
toCanvas.LineTo(x, BoundCanvas.Bottom - 7);
toCanvas.MoveTo(x, BoundCanvas.Bottom - 5);
toCanvas.LineTo(x, BoundCanvas.Bottom - 4);

//My Code to Draw text
toCanvas.Font.Color := clRed;
toCanvas.Font.Name := 'Times New Roman';
toCanvas.Font.Size := 20;
toCanvas.TextOut(BoundCanvas.Left+10,BoundCanvas.Top+50,'Delphi');
end;

if the code used with Image.Canvas,the font Size is correct

Image1.Canvas.Font.Color := clRed;
Image1.Canvas.Font.Name := 'Times New Roman';
Image1.Canvas.Font.Size := 20;
Image1.Canvas.TextOut(1,2,'Delphi');

sorry,my english is poor