Interest rates on short-term T-bills edged down at the latest auction after a sharp jump last week. The Treasury sold $6.4 billion in new three-month bills at an average discount rate of 6.49%, down from 6.79% at a delayed auction held last Thursday. Another $6.4 billion was sold in six-month bills at an average discount rate of 6.96%, down from 7.07% at Thursday's auction. The rates this week on three-month bills were the lowest since Sept. 14, when they averaged 6.32%. The rates on six-month bills were the lowest since 6.83% at last Monday's auction. The discount rate reflects the price discount received when government securities are purchased at less than face value.