FLC OF A BA31 OPERATED OVER ONE OF THE COMPANY INSPECTION INTERVALS DUE TO MISREADING THE TIMES SHOWN IN THE ACFT LOGBOOK.

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THE COMPANY HAS A PREVENTIVE MAINT PROGRAM THAT INCLUDES PERIODIC INSPECTIONS AT CERTAIN TIME INTERVALS. WE HAVE A REQUIRED INSPECTION EVERY 5 DAYS AND A 3 DAY OR 72-HR INSPECTION WITHIN EACH 5 DAY INSPECTION. THE INSPECTIONS ARE SIGNED OFF IN THE ACFT LOGBOOK. THERE IS ALSO A 50 FLT HR REQUIREMENT BTWN INSPECTIONS; WHICH CAN BE EXCEEDED PER THE COMPANY MAINT MANUAL. (I WAS NOT COMPLETELY AWARE OF THE 50 HR REQUIREMENT). IT IS THE CAPT'S RESPONSIBILITY TO CHK THE LOGBOOK PRIOR TO FLT TO MAKE SURE ALL THESE REQUIREMENTS ARE MET. DURING ONE OF OUR USUAL QUICK 20 MIN TURNS AND CREW CHANGE THE CAPT HELPED SPD THINGS ALONG BY SPLITTING UP PREFLT DUTIES. I PREFLTED THE EXTERIOR AND CABIN WHILE THE CAPT CHKED THE COCKPIT AND LOGBOOKS. I RETURNED AND PREFLTED MY ITEMS IN THE COCKPIT ANYWAY. WE BOARDED UP THE PAX AND DEPARTED. THE CAPT CHKED THE LOGBOOK AND THE ACFT WAS WITHIN THE 5 DAY (72 HR) INSPECTIONS; BUT DUE TO SLOPPY RECORDING OF NUMBERS AND SHORT GND TIME; THE CAPT APPARENTLY MIS-ADDED A NUMBER AND SO THE ACFT HAD APPARENTLY EXCEEDED THE 50 HR INSPECTION REQUIREMENT PRIOR TO THE FLT. I FEEL THE MAINT DEPT SHOULD HAVE DOUBLE-CHKED THEIR RECORDING AND TRACKING PROCS. THE SLOPPY OR MISTAKEN RECORDING OF NUMBERS LED TO THIS; AS DID THE QUICK TURNS. ANYONE CAN MAKE A SLIGHT ADDITION MISTAKE; EITHER PRIOR TO THE TRIP; AT THE TIME OR DOWN THE LINE.