The total number of panels "lines" that the drop down control is to occupy on the panel or window.
For styles A and B this value indicates the number of lines that the drop down should occupy when the user has dropped it down.
For styles C and D this value indicates the number of lines that the drop down control should permanently occupy on the panel.
This argument must be a valid number in the range 1 to 20. Values outside this range are ignored and the default value is used.
The value is specified in panel "lines", where a panel is up to 24 lines long. The actual number of items that can be visualized in the drop down depends upon the height of the font being used.
The default length is the least of
a) no. of items in the List;
b) remaining lines on the Panel.