FLC OF B737 SET ALTIMETER PASSING THROUGH FL180 ERRONEOUSLY RESULTING IN 1000 FT DIFFERENCE FROM ASSIGNED ALT.

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HAVE YOU EVER LOOKED AT SOMETHING AND WHAT YOU SAW WAS COMPLETELY DIFFERENT THAN WHAT WAS ACTUALLY THERE? THIS IS THE ONLY WAY I CAN DESCRIBE WHAT HAPPENED TO OUR FLT. I HAD NOTED TO MYSELF AT OUR FLT PLANNING EARLIER WHAT A LOW ALTIMETER SETTING IT WAS FOR SFO THIS DAY (29.42). ACTUALLY; THE ALTIMETER WAS 30.42 AND I EITHER MISREAD IT; GLANCED OVER IT OR JUST PLAIN DIDN'T REGISTER IT. IN ANY EVENT; I REMEMBERED 29.42 INSTEAD OF THE RPTED ACTUAL 30.42 PRESSURE AT SFO; OUR TKOF ARPT. CLBING THROUGH FL180; I HAD A CHANCE TO CATCH THE MENTAL MISTAKE WHEN I WENT TO RESET MY ALTIMETER TO 29.92. IT MUST BE NOTED THAT AT THIS POINT MY ALTIMETER WAS SET PROPERLY TO 30.42. HOWEVER; THINKING 29.42 AND I MUST CONFESS ONLY LOOKING AT THE .42 PART OF THE KOHLSMAN WINDOW; I NATURALLY TURNED THE SETTING 'UP' TO 29.92 FROM MY PRECONCEIVED 29.42. WHAT I ACTUALLY DID OF COURSE WAS TO SET 30.92 IN MY ALTIMETER CAUSING US TO BE 1000 FT OFF OF OUR ASSIGNED ALT OF FL330 AT LEVELOFF. OBVIOUSLY; I HAD MANY CLUES AS TO MY ERROR; BUT FOR WHATEVER REASON; NONE REGISTERED UNTIL ATC ASKED OUR ALT AND THEN GAVE US A DSCNT TO A LOWER ALT. I DON'T BELIEVE THERE WERE ANY CONFLICTS WITH OTHER TFC AND FOR WHATEVER REASON THE FO AND POSSIBLY THE CTLR DID NOT CATCH MY MISTAKE EITHER. AS WE APCHED FL240; THE FO CALLED FOR ME TO LEVEL OFF; BUT I THOUGHT WE HAD 1000 FT TO GO. THE CONFUSION LED TO THE DISCOVERY OF MY MISSET ALTIMETER. WE LEVELED PROPERLY AND RESET MY ALTIMETER PROPERLY. I CANNOT EXPLAIN WHY ALL THESE LAPSES OCCURRED AS THE FO AND I ARE USUALLY VERY CAREFUL TO FOLLOW SOP AND STAY AWARE SITUATIONALLY; BUT IT DID.