How many flights of Endeavor Air Inc. were faster than scheduled on 2018/8/31?
Endeavor Air Inc. refers to Description = 'Endeavor Air Inc.: 9E'; faster than scheduled refers to ACTUAL_ELAPSED_TIME < CRS_ELAPSED_TIME; on 2018/8/31 refers to FL_DATE = '2018/8/31';
SELECT SUM(CASE WHEN T1.ACTUAL_ELAPSED_TIME < CRS_ELAPSED_TIME THEN 1 ELSE 0 END) AS count FROM Airlines AS T1 INNER JOIN `Air Carriers` AS T2 ON T1.OP_CARRIER_AIRLINE_ID = T2.Code WHERE T1.FL_DATE = '2018/8/31' AND T2.Description = 'Endeavor Air Inc.: 9E'