CTLR MADE MISTAKE WHEN GIVING CLRNC TO DESCEND.

Narrative

FLYING AS F/O WITH CAPT HANDLING RADIO. ON DESCENT FOR SJC; CLRED TO CROSS SNS AT OR BELOW 190 DESCEND TO 12000. CHANGED SECTOR FREQ WITHIN OAK CENTER; CAPT REPEATED CURRENT DESCENT CLRNC AND RESTRICTION. AS I RECALL WE WERE ALREADY NEAR 200 AND ABOUT 20 DME SOUTH OF SNS. WE BOTH UNDERSTOOD OAK CTR TO CLR US TO TURN RIGHT 10 DEG FOR VECTOR TO SJC LOC AND MAINTAIN 8000'. I REACHED; WITH CAPT WATCHING; AND RESET ALT ALERT FROM 12000 TO 8000. I CONTINUED USING ROUGHLY THE USUAL CLRNC PARAMETERS SJC 55D AT 12000 AND SJC 25D AT 8000. SLOWING AT ROUGHLY 10000' OAK CTR ASKED ALT. CAPT REPORTED 'SLOWING AT 10 FOR 8.' NOTHING FURTHER FROM OAK CTR UNTIL CAPT ASKED IF THEY HAD LOST OUR ALT REPORTING. OAK CTR SAID NO BUT WE HAD BEEN CLRED TP 12000. CAPT SAID WE HEARD AND ACKNOWLEDGED 8000. NOTHING FURTHER FROM OAK CTR UNTIL CAPT PROMPTED; ASKING WHERE THEY WANTED US NOW. CLRED TO 8000; WE CONTINUED. IT WAS AS IF INCIDENT DISRUPTED FURTHER HANDLING EVEN INTO BAY APPROACH BECAUSE FURTHER DESCENTS WERE ALL LATER THAN NORMAL PROFILE. THIS CAUSED US TO BE HIGH ON PROFILE ALL THE WAY TO SJC. (OAK CTR LATER VERIFIED CTLR ERROR AND COUNSELED HIM). CALLBACK CONVERSATION REVEALED THE FOLLOWING ADDITIONAL INFO: THE CAPT OF THE FLT CALLED THE CENTER AFTER LANDING. HE WAS TOLD THAT AN INVESTIGATION HAD BEEN MADE BY THE CTLR. THE CTLR HAD MEANT TO STOP THEIR DESCENT AT 12000; BUT HAD MISTAKENLY SAID 8000. NO TFC CONFLICT OR LOSS OF SEP RESULTED.