B757 LNDG AT ATL ANTICIPATES ALT CLRNC AND DSNDS BELOW ASSIGNED ALT.

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DURING ARR INTO ATLANTA ON SINCA ARR (ATL 128 DEG RADIAL); WE CROSSED THE HUSKY FIX AT 14000 FT AND RECEIVED FURTHER DSCNT TO 12000 FT. I WAS ANTICIPATING CLRNC TO DOWNWIND HDG OF APPROX 270 DEGS FURTHER DSCNT TO 7000 FT. PRIOR TO LEVELING AT 12000 FT; ATC CLRED US FOR FURTHER DSCNT TO WHAT I HEARD AS 'DSND TO 7000 FT' AND I ENTERED 7000 FT IN THE ALT WINDOW ON THE AUTOPLT PANEL (AUTOPLT WAS ON) AS THE FO ACKNOWLEDGED AND READ BACK TO ATC AS 'DSND TO 7000 FT.' AS WE DSNDED THROUGH 10500 FT; WE SAW A CLBING DEP ACFT VISUALLY AFTER A TCASII ALERT. APCH CTLR QUERIED US FOR OUR ALT AND FO (PNF) RESPONDED WITH 'DSNDING TO 7000 FT; TFC IN SIGHT.' CTLR RESPONDED WITH 'CLB TO 11000 FT; MAINTAIN VISUAL SEPARATION.' WE CLBED TO 11000 FT; AND SHORTLY LATER; RECEIVED CLRNC TO 'TURN TO 275 DEGS; DSND TO 7000 FT.' I BELIEVE THIS OCCURRENCE WAS A HEARBACK/READBACK PROB COUPLED WITH SIMILAR SOUNDING ALTS OF SEVEN/ELEVEN. TO PREVENT RECURRENCE; I BELIEVE IN THIS CASE WHERE ELEVEN AND SEVEN THOUSAND FT ALT CLRNCS ROUTINELY COME SUBSEQUENTLY TO EACH OTHER; THAT THE ELEVEN THOUSAND FT CLRNC SHOULD BE GIVEN AS 'DSND TO ONE-ONE ELEVEN THOUSAND' TO FURTHER DISTINGUISH IT FROM THE 'DSND TO 7000 FT' CLRNC.