This property determines the number of rows that will be treated as column headings. When it is set to zero, the grid columns will not have headings. When it is set to a positive value, this value will correspond to the number of rows that will be treated as column headings. For example, if you set the value of this property to 2, the first two records in the grid will be headings. Headings are always visible and can be colored differently from the body of the grid. Specifying more column headers than rows visible in the grid has undefined effects.
This property effectively supersedes the COLUMN-HEADINGS style. If you specify COLUMN-HEADINGS, a NUM-COL-HEADINGS value of 0 is treated as if it were 1. The COLUMN-HEADINGS style has no effect when NUM-COL-HEADINGS is set to greater than zero. This rule provides backwards compatibility with COLUMN-HEADINGS while still allowing for a multi-row column header.