MD88 FLC DSNDS BELOW CLRED TO ALT WITH WRONG ALT SETTING. CREW HAD OBTAINED ALT SETTING FROM ATIS PRIOR TO DSCNT FROM FL180 WITH NO OTHER VERIFICATION BEING MADE LATER. FLC DISTR WITH ARR CHANGES.

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ON ARR (KASPR 1) TO MSP; APCH DSNDED US TO 7000 FT. AFTER WE LEVELED AT 7000 FT; APCH ASKED US OUR ASSIGNED ALT. WE ANSWERED 7000 FT AND WE WERE LEVEL. THEY SAID WE SHOWED 6000 FT. THEY INFORMED US THE ALTIMETER WAS 29.36. WE HAD COPIED AND SET 30.36 OFF OF ATIS (MSP). WE STARTED TO CLB TO 7000 FT; BUT APCH DSNDED US TO 4000 FT. THERE; FORTUNATELY; HAD NOT BEEN A CONFLICT. WE (I) HAD GOTTEN 30.36 OFF OF MSP ATIS. EITHER IT HAD BEEN WRONG; OR I HAD MISHEARD THE ALTIMETER. ON THE GND; THE ATIS HAD ALREADY BEEN CHANGED; SO WE NEVER DETERMINED WHICH. UNFORTUNATELY; ON OUR ARR INTO MSP; ZMP HAD NOT GIVEN US AN ALTIMETER IN OUR DSCNT BELOW 18000 FT. SINCE WE HAD MSP ATIS ALTIMETER; WE NEVER QUESTIONED THEM FOR AN ALTIMETER; MISSING OUR CHANCE TO CATCH AND CORRECT THE DISCREPANCY. GETTING AN ALTIMETER VERIFICATION FROM CTR ON DSCNT; IS A XCHK ON ATIS ALTIMETER I WILL NO LONGER FOREGO. SUPPLEMENTAL INFO FROM ACN 364470: MY DSCNT TO 7000 FT WAS ALMOST CONTINUOUS WITH STEPDOWNS ASSIGNED PRIOR TO OR JUST AS WE REACHED OUR PREVIOUSLY ASSIGNED ALT. AN UPDATED ALTIMETER SETTING WAS NOT PROVIDED OR REQUESTED WHEN WE WERE CLRED BELOW FL180. I BELIEVE WE MISSED THIS OPPORTUNITY TO CATCH THE WRONG SETTING BY PREOCCUPATION WITH SIMULTANEOUS FREQ CHANGE AND/OR ONE OF TWO RTE CHANGES AT 'DIRECT TO' POINTS CLOSER IN ON THE ARR BEING FLOWN.