This field specifies how many characters not to update within the rectangle. The value you specify for PPB-Rectangle-Offset is the position within the specified rectangle (defined by PPB-Update-Width and PPB-Update-Height) at which you wish to start updating the panel. If you intend to update the entire rectangle, you should set the PPB-Rectangle-Offset field to 0.
You can choose to update an irregular-shaped area of a rectangle by specifying values for both the PPB-Update-Count and PPB-Rectangle-Offset fields.
If you want to update the unshaded part of the panel you have to use PPB-Update-Count and PPB-Rectangle-Offset to specify how many characters are to be updated, and where the updating is to start: