FLC OF AN MLG OVERSHOT PUBLISHED XING ALT OR DID NOT MAKE ASSIGNED XING ALT SINCE THE XING ALT WAS NOT CLARIFIED AFTER THE FACT BY ATC.

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DURING INITIAL DSCNT INTO SNA WE WERE GIVEN CLRNC TO CROSS PSP AT FL240 BY ZLA. AT FL240 WE WERE NOW CLRED DIRECT TO BANDS INTXN ON THE E SIDE ARR TO CROSS BANDS AT 12000 FT. (WE THINK) I READ BACK BANDS AT 12000 FT AND THE CAPT SELECTED 12000 FT IN THE MCP ALT WINDOW. CAPT AND I STARTED TO DISCUSS THIS ALT AS E SIDE ARR SHOWS BANDS XING AT 14000 FT. WE WERE INTERRUPTED BY CTR WHO HANDED US OFF TO SOCAL APCH CTL. I CHKED IN WITH SOCAL DSNDING TO 12000 FT. I THINK WE WERE OUT OF 14000 FT AND HAD JUST COMPLETED THE IN-RANGE CHKLIST. INDICATED TO SOCAL THAT WE MIGHT NOT BE ABLE TO MAKE THE 12000 FT XING AT BANDS. WE DID. AFTER LEVEL OFF; SOCAL CTLR ASKED IF WE WERE CLRED TO CROSS BANDS AT 14000 FT. I SAID; 'NO; THAT 12000 FT IS WHAT WE HEARD.' SOCAL NOW CLRED US TO CROSS KAYOH ON THE E SIDE ARR AT 7000 FT. NOTE THAT PUBLISHED XING ALT IS 8000 FT. REST OF APCH WAS UNEVENTFUL. RECOMMENDATION: WHEN CLRED DIRECT TO A PUBLISHED FIX WITH A PUBLISHED XING ALT ALWAYS ASSIGN THE ALT THAT IS PUBLISHED. CTR MAY HAVE DONE JUST THAT AND WE MISUNDERSTOOD; BUT SOCAL DID ASSIGN A DIFFERENT ALT THAN PUBLISHED.