CORP MDT READ BACK WRONG ALT. CTLR DID NOT CORRECT WRONG READBACK.

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RECEIVED CLRNC FROM ZHU ON 134.5 TO CROSS MARIT INTXN AT 12000'. I WROTE CLRNC ON MY NOTEPAD AND READ BACK RESTRICTION TO CROSS MARIT AT 12000'. (MARIT IS AN INTXN ON THE STRUCK 6 ARR FOR HOU HOBBY.) ZHU MADE NO COMMENT ON MY READBACK. WE WERE THEN TURNED OVER TO HOU APCH ON 124.35. I CHKED IN; ADVISING WE WERE AT 12000' AND HAD CURRENT ATIS. HE QUESTIONED OUR ASSIGNED ALT AND I REPLIED THAT OUR ASSIGNMENT WAS 12000' AT MARIT AS RECEIVED; COPIED AND READ BACK TO ZHU. HE SAID WE SHOULD BE AT 10000' AND HE WOULD CHK WITH ZHU FOR VERIFICATION. HE THEN CAME BACK ON FREQ AND SAID THAT ZHU SAID THEY HAD ASSIGNED US 10000'. WE (BOTH PLTS) AGREED WE HAD BEEN ASSIGNED 12000'. I HAD COPIED THE ASSIGNED ALT ON MY NOTEPAD AND THEN READ BACK THE ASSIGNED ALT AS 12000'. ZHU MADE NO COMMENT OR ATTEMPT TO CORRECT; IF INDEED WE HAD MISUNDERSTOOD THE CLRNC. THERE WAS NO TFC CONFLICT OR ALERT. HOU APCH SAID; 'THERE'S NO PROB.' RECOMMENDATION: LISTEN TO ALL READBACKS. THIS APPLIES TO ALL OF US--PLTS; CTLRS; EVERYBODY. DO NOT HESITATE TO ASK FOR VERIFICATION OF ANY HDG; ALT; AIRSPD; ETC.