<summary>
The underline position value of the font face in font design units.
Underline position is the position of underline relative to the English baseline.
The value is usually made negative in order to place the underline below the baseline.
</summary>
<summary> The underline position value of the font face in font design units. Underline position is the position of underline relative to the English baseline. The value is usually made negative in order to place the underline below the baseline. </summary>