TRACON DEP CTLR AMENDS ALT OF DEP DC9 FOR TFC. WHEN TFC CLR; CTLR REASSIGNS HIGHER ALT; 10000 FT; BUT CTLR MISSES INCORRECT READBACK OF 16000 FT; XFERRING DC9 TO ARTCC. PLT STATES CLBING TO 16000 FT TO ARTCC; BUT CTLR ALSO MISSES CLBING ALT. ARTCC CTLR OBSERVES HIGHER ALT; AND RECLRS ACFT BACK DOWN TO 10000 FT.

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PLT OF DC9 WAS ISSUED HDG 265 DEGS DIRECT BUFFALO WHEN ABLE; CLB AND MAINTAIN 10000 FT. PLT READ BACK 16000 FT. INCORRECT READBACK NOT CAUGHT BY ATC. SUPPLEMENTAL INFO FROM ACN 410076: I CHKED IN WITH ROC DEP SAYING WE WERE CLBING TO 10000 FT. SHORTLY AFTER HE INSTRUCTED US TO LEVEL AT 5000 FT FOR TFC AND GAVE US A HDG TO FLY. SUPPLEMENTAL INFO FROM ACN 410080: WHEN WE WERE CLR OF THE TFC; THEY GAVE US A CLB TO 16000 FT. THIS WAS READ BACK AS SUCH BY THE COPLT; AND SET 16000 FT IN THE ALT ALERT WINDOW. DEP CTL THEN HANDED US OVER TO ZOB. THE COPLT CHKED US IN AS 'OUT OF 8000 FT FOR 16000 FT.' CLBING THROUGH APPROX 10600 FT; THE CTR CTLR ASKED US IF WE WERE LEVELING AT 10000 FT. WE RESPONDED NO; THAT WE HAD BEEN CLRED TO 16000 FT. HE TOLD US TO MAINTAIN 10000 FT; WHICH WE IMMEDIATELY DSNDED TO. THE CTLR ASKED US WHO CLRED US TO 16000 FT; AND WE TOLD HIM THE DEP CTLR. HE TOLD US IT WAS A MISTAKE AND THAT WE SHOULD HAVE ONLY BEEN CLRED TO 10000 FT. AS FAR AS WE WERE CONCERNED; WE HAD BEEN GIVEN CLRNC TO 16000 FT. IF WE WERE ISSUED 10000 FT; NEITHER OF US HEARD THAT. WE THOUGHT THAT HE SAID 16000 FT. THE COPLT ALSO CHKED IN WITH ZOB AS 'CLBING TO 16000 FT.' THIS IS A GOOD EXAMPLE OF HOW IMPORTANT IT IS FOR US AS PLTS TO CAREFULLY LISTEN TO THE CLRNCS (IN THE EVENT THAT HE DID GIVE US 10000 FT AND WE THOUGHT THAT IT WAS 16000 FT); AND HOW IMPORTANT IT IS FOR THE CTLRS TO LISTEN TO THE READBACK IN CASE THERE IS A DISCREPANCY IN WHAT HE SAID AND WHAT THE PLT HEARD.