ACR X WRONG ALTIMETER SETTING DSNDED BELOW ASSIGNED ALT. ALTDEV. PLTDEV.

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CAPT WENT TO BATHROOM. ACR X WAS LEVEL AT FL190 AND RECEIVED A CLRNC TO 17000 FT. THE ATIS FORM DID RECORD 29.61 INCHES AND THE CTLR SAID 29.61 INCHES; YET I MISTAKENLY DIALED IN 30.61 INCHES ON MY ALTIMETER. IMMEDIATELY AFTER THAT THE AUTOPLT CLICKED OFF FOR UNKNOWN REASONS. I RESTORED IT AND CONTINUED THE DSCNT. THE 700 FT (APCHING ALT) WARNING WENT OFF AND IMMEDIATELY THEREAFTER; THE AUTOPLT CLICKED OFF AGAIN. I RESTORED IT AGAIN; JUST AS THE CAPT WALKED BACK IN. I NOTICED THAT THE ACFT WAS LEVELING OFF AT AN ALT INCONSISTENT WITH THE ALERTER OR THE CLRNC AND IMMEDIATELY CHKED THE CAPT'S ALTIMETER SETTINGS (STILL ON 29.92 INCHES) BECAUSE ON SOME OF THE EX-ACR A300'S; THE 4TH ALTIMETER (ON CAPT'S SIDE) DROVE THE AUTOPLT #2. THE CAPT REACHED OVER HIS SEAT TO SET HIS ALTIMETERS (2 PLUS STANDBY) WHEN ATC INFORMED ME TO CLB BACK TO 17000 FT. AT THAT TIME THE CAPT NOTICED THAT MY ALTIMETER WAS SET 1000 FT OFF. I CORRECTED THE ALTIMETER AND THE ALT. SUPPLEMENTAL INFO FROM ACN 293076: I STEPPED OUT OF COCKPIT APPROX 1 MIN WHEN WE STARTED A DSCNT. THE DSCNT DIDN'T FEEL SMOOTH/NORMAL SO I CAME BACK TO COCKPIT IMMEDIATELY. I ASKED FO (HE WAS HAND FLYING ACFT NOW) WHAT WAS WRONG. HE STATED ACFT WAS TRYING TO LEVEL OFF AT TOO LOW AN ALT AND HE WAS OVERRIDING IT. MY ALTIMETER READ 16400 FT DSNDING (29.92) AND HIS READ APPROX 17100 FT DSNDING (30.60). ATIS CARD SAID 29.60. I IMMEDIATELY ORDERED HIM TO CLB. 17000 FT WAS SET IN AUTOPLT ALT WINDOW. ATC ASKED OUR ALT AS WE STARTED UP. I RESPONDED CLBING TO 17000 FT. ATC RESPONDED 'THAT'S YOUR ASSIGNED ALT.' FO HAD ACCEPTED DSCNT FROM FL190 TO 17000 FT; BUT SET HIS ALTIMETER AT 30.60 (WX WAS CLR/COLD AND HE THOUGHT HIGH PRESSURE WAS IN AREA). HE IS A GOOD PLT BUT WAS TIRED AND IT WAS LAST LEG OF A 3 DAY TRIP IN GOOD WX.