Turn the Delay B knob until the display reads . A . B . C . D (approximately 1 o'clock on the knob).  Set the Delay A knob to 1200 ms.  The delay times of four voices are spaced evenly at that setting, with the longest delay time being displayed and adjusted by the Delay A knob.   (Somewhat counterintuively – this will indicate the Delay D value).  That should result in Delay A  = 300 ms., Delay B = 600 ms., Delay C = 900 ms., and Delay D at the 1200 ms. value.