The Division has taken the position that the exemption provided by section 13(b)(17) of the Fair Labor Standards Act will be deemed applicable even though some nonexempt work (that is, work of a nature other than that which characterizes the exemption) is performed by the employee during the workweek, unless the amount of such nonexempt work is substantial. For enforcement purposes, the amount of nonexempt work will be considered substantial if it occupies more than 20 percent of the time worked by the employee during the workweek.