topMargin (USHORT)
The value in this field defines the top unprintable area for this input. The top margin is defined as that area above the first printable line written in the marking direction. The units for this value are specified by lengthUnits in the PRTDEVCHAR data structure. A value of hex 'FFFF' indicates that the printer does not have, nor can it determine, this value.
Note: This value specifies the limitation of the printing mechanism and also indicates that particular interpreters may place additional limitations on the margins.