FLC OF AN ACR MLG ENTERED THE WRONG HOLDING PATTERN ASSIGNED BY ATC.

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AFTER TKOF AT PHL; WE WERE CLRED TO IAH VIA DIRECT MXE; AS PREVIOUSLY CLRED; MAINTAIN 10000 FT. AS WE APCHED MXE (THE NORMAL HDOF POINT TO ZNY) WE ASKED IF IT WAS TIME FOR A FREQ CHANGE AND WERE TOLD TO STANDBY. AFTER PASSING MXE; WE CONTINUED ON OUR RTE; OUTBOUND ON THE 278 DEG RADIAL OF MXE. WE THEN WERE ISSUED THE FOLLOWING CLRNC: 'CLRED TO MXE; HOLD W ON THE 278 DEG RADIAL; L TURNS; 10 MI LEGS; MAINTAIN 1000 FT; WITH AN EXPECT FURTHER CLRNC OF ABOUT 30 MINS LATER. THE FO READ BACK THE CLRNC AND BEGAN TO ENTER THE HOLD IN THE FMS COMPUTER. THE FO AND I AGREED ON THE HOLDING ENTRY PROC; BUT I FELT SURE THAT THE HOLDING INSTRUCTIONS WERE INCORRECT. FREQ CONGESTION KEPT US FROM QUESTIONING HIS INSTRUCTIONS BEFORE IT WAS TIME TO BEGIN THE PATTERN ENTRY PROC. THE CTLR WAS WORKING 3 ACFT BEHIND US; ALSO HDG TO MXE AT 10000 FT; IN ADDITION TO SEVERAL OTHER ACFT. AS WE MADE A R-HAND TURN BACK TOWARD MXE TO COMPLETE THE ENTRY; THE CTLR SAID HE CLRED US FOR L TURNS IN THE HOLD. I TRIED TO EXPLAIN WHAT WE WERE DOING; BUT THE CTLR DID NOT UNDERSTAND. I SAID THAT I WOULD CALL HIM ON THE PHONE LATER; TO EXPLAIN IN DETAIL; AND ASKED HIM WHAT HDG HE WANTED US TO FLY. WE WERE GIVEN A R TURN; BACK TO THE W AND WERE HANDED OFF TO CTR. THE REST OF THE FLT TO HOUSTON WAS UNEVENTFUL.