The default value is 50.

Valid values are 0 to 100.

This option is used when DetectColor is used to locate colored regions on the page. In some cases, regions of color, such as highlighter over text, will be broken down into many smaller regions of color. A value of 100 will result in no boxes being combined, even if one box is located entirely within another; a value of 0 will result in all boxes that intersect to any degree being combined.

Reference