To reset the mercury lamp count to zero: long press the DS button until it displays the hours of use of the mercury lamp, and then press the right down arrow button to reset to zero.
Mercury lamp counting to zero: long press the DS button to display the service hours of mercury lamp, and then press the down arrow button on the right to zero.
Mercury lamp counting to zero: press the DS button for a long time until it shows the working hours of mercury lamp, and then press the down arrow button on the right to zero.