"Assumed temperature" is a method, or procedure, applied to a normal maximum thrust RTOW chart, when appropriate, to obtain a safe level of reduced thrust for the present takeoff. . .. .In essence, the (chart entry) OAT is presumed to be higher than the actual OAT to take advantage of a weight margin below the maximum for the day. The procedure is conservative as the aircraft's performance will reflect the actual OAT, not the presumed higher value. The end result is that the operator gains a small cumulative maintenance (cost) benefit associated with lower exhaust temperatures for the takeoff.