<summary>
Specifies the vertical distance from the black box's bottom edge to the advance height.
Positive when the bottom edge of the black box is within the layout box.
Negative when the bottom edge of black box overhangs the layout box.
</summary>
<summary> Specifies the vertical distance from the black box's bottom edge to the advance height. Positive when the bottom edge of the black box is within the layout box. Negative when the bottom edge of black box overhangs the layout box. </summary>