why pt font is smaller than px font in JTextPane when using the same number? :     public static void main(String[] args) {
        JFrame frame = new JFrame("Test");
        JTextPane pane = new JTextPane();
        pane.setContentType("text/html");
        pane.setText("<html>"
                + "<head>"
                + "<title> New Document </title>"
                + "</head>"
                + "<body>"
                + "<div style=\"font-size:20pt\">bbbbbbbb-20pt</div>"
                + "<div style=\"font-size:20px\">bbbbbbbb-20px</div>"
                + "</body>"
                + "</html>");
        frame.add(pane, BorderLayout.CENTER);
        frame.setSize(500, 600);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
the frame show:
[enter image description here][1]


but the same content of html show in browser are different:
[enter image description here][2]


  [1]: https://i.stack.imgur.com/XNaVF.jpg
  [2]: https://i.stack.imgur.com/kNta6.jpg