Represents the "RD" entry of the caret annotation object.

It is an optional entry defined as part of the PDF 1.5 specification.

It contains a RectangleElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 180, page 404.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 183, page 490.

The rect difference insets the drawn caret symbol from the annotation's Rect, providing visual space within the overall bounding rectangle.