ACR MLG OVERSHOT ALT ON DESCENT.

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ZNY GAVE US AN ALT RESTRICTION TO CROSS 20 E OF ETG. I THOUGHT THE ALT GIVEN WAS FL200. WE WERE LEVEL AT FL280 AND I WAS FLYING THE AIRPLANE. THE CAPE ANSWERED THE RADIO CALL AND WROTE ON HIS SCRATCH PAD. I SET 20000' IN THE ALT ALERTER. THE CAPT WAS ENGROSSED IN READING A MAGAZINE AND DIDN'T LOOK UP FROM HIS READING TO CONFIRM THE ALT I HAD SET. I STARTED MY DSCNT USING 1500 FPM TO LOSE THE 8000' BY 20 MI E OF ETG. AFTER LEVELING AT FL200; ZNY CALLED AND ASKED WHAT ALT WE WERE AT. THE CAPT LOOKED UP TO SEE THE ALT. HE THEN ANSWERED CENTER WITH '200 AS ASSIGNED.' CENTER RESPONDED WITH; 'THE ALT WAS 220.' THE CAPT ANSWERED WITH; 'OK; OUT OF 200 FOR 220.' CENTER THEN TOLD US TO STAY AT FL200 SINCE WE WERE ALREADY THERE. THE CAPT LOOKED AT WHAT HE HAD WRITTEN ON HIS SCRATCH PAD. IT SAID '20E22.' HE TOLD ME HE KNEW THE ALT GIVEN WAS FL220 BECAUSE THEY ALWAYS GIVE 20 E OF ETG AT FL220. I AM FAIRLY NEW AT AIRLINE FLYING AND NOT FAMILIAR WITH WHAT THEY; 'ALWAYS GIVE IN A CLRNC.' THIS INCIDENT WAS A CASE IN WHICH THE COPLT MISREAD A CLRNC AND THE CAPT WAS NOT PAYING ATTN TO THE COCKPIT ACTIVITIES. I FEEL THAT A LACK OF CREW COORD CAUSED THE INCIDENT TO OCCUR. I AM SURPRISED THAT ZNY DIDN'T NOTICE OUR ALT DEVIATION UNTIL WE WERE LEVELED OFF 2000' FROM THE ASSIGNED ALT. SUPPLEMENTAL INFO FROM ACN 97450: MY F/O WAS FLYING THE ACFT AND I TOOK FOR GRANTED HE RECEIVED THE CORRECT CLRNC. BY THE TIME I REALIZED; HE DSNDED TO FL200. AT THAT TIME WE WERE QUESTIONED BY ATC.