ACR WDB DEPARTED ALT ON APCH PRIOR TO REACHING PROPER FIX.

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ON LOC 30 APCH TO MIA INTL DSNDED TO 3000' MSL AT WHAT I BELIEVED TO BE OLDDE FIX 10.7; BUT WAS ACTUALLY APPROX 8 NM FURTHER OUT. STARTED DSCNT TO 1500' MSL TO CROSS FAF AT BIRDD AT 1500' MSL. BECAUSE I WAS READING DME OFF OF BISCAYNE BAY VICE LOC I WAS LOWER THAN I SHOULD HAVE BEEN. APPROX 5 NM OFF OF BISCAYNE BAY I LEVELED AT 2100' BECAUSE THINGS DIDN'T LOOK RIGHT; AT WHICH TIME TWR ASKED US IF OUR ALT XING OLDDE WAS 3000' AND WE BELIEVED WE HAD CROSSED OLDDE AT 3000' AND REPLIED AFFIRMATIVELY. AS THE APCH CONTINUED I MAINTAINED ALT AT 2100' UNTIL A VISUAL G/S TO 30 HAD BEEN ESTABLISHED AND I BELIEVE THE PROB STEMS FROM THE FACT THAT BOTH MYSELF AND THE CAPT BEING RELATIVELY NEW IN THE ADVANCED COCKPIT AND WORKING WITH AN FMS NAV SYS CONFUSED THE DME (LOC) READOUT WITH DME READOUT OF THE VOR. UPON CLOSER SCRUTINY WE DETERMINED THAT THE ACTUAL READOUT OF THE DME WAS ON THE PFD CRT SCREEN (LOWER LEFT) AND NOT ON THE RMI DME READOUT AS IT ALSO SHOULD HAVE BEEN. ACCORDING TO OUR OPERATING MANUAL; THE DME READOUT OF THE ILS/DME FREQ SELECTOR SHOULD BE DISPLAYED ON THE RMI DME DISPLAY AS WELL AS ON THE PFD DISPLAY IF THE EFIS PANEL SELECTOR SWITCH IS SELECTED TO ILS POS; AS IT WAS. THE VOR DME READOUT OF BISCAYNE BAY SHOULD ONLY HAVE BEEN PRESENT HAD THE EFIS PANEL SELECTOR SWITCH BEEN SELECTED TO THE VOR POS. THE PROB POSED NO THREAT TO SAFETY OF FLT DUE TO TREMENDOUS VMC CONDITIONS AND VIS. SUPPLEMENTAL INFO FROM ACN 97452: A CONTRIBUTORY FACTOR IS THE FACT THAT BOTH PLTS ARE NEW TO EFIS ACFT; AND WERE USING THE OLD FAMILIAR DME IN THE RMI. THE DME IN THE PFD WAS READING PROPERLY OFF THE LOC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATED THEY HAVE CHKED PFD SINCE AND HAVE THE SAME INDICATIONS. THE DME IN THE RMI DOES STAY ON THE TUNED VOR STATION AND DOES NOT SWITCH TO ILS. WITH PFD EFIS SWITCH ON ILS THE READOUT ON THE PFD IS THE ILS DME READOUT AND PLT ADMITTED HE KNEW THAT IS WHAT THEY SHOULD HAVE BEEN LOOKING AT. STILL THINKS THE MANUAL READS WRONG AND WILL BRING THAT UP TO COMPANY.