FLT CREW REPORTS MISUNDERSTANDING CONTROLLER ISSUING NEW RWY ASSIGNMENT AND NEW ALTITUDE. FLT CREW SETS QNH PRIOR TO DESCENDING BELOW TRANSITION LEVEL.

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ON DESCENT INTO ZGGG; WE LEVELED OFF AT THE ASSIGNED ALTITUDE (IN METERS) AND HAD RESET OUR ALTIMETERS TO THE LOCAL ALTIMETER SETTING BECAUSE WE THOUGHT WE HEARD THE CONTROLLER USE THE PHRASE 'NONSTANDARD' WITH THE ALTITUDE ASSIGNED. A FEW MINUTES LATER; THE CONTROLLER TOLD US THAT HE SHOWED US 100 METERS LOW AND WE CONFIRMED THAT WE WERE AT THE ASSIGNED ALTITUDE. WE CONFIRMED THAT ALL OF ALTIMETERS WERE AT THE LOCAL ALTIMETER SETTING AND ASKED THE CONTROLLER AGAIN FOR HIS READING OF OUR ALTITUDE. WE DIDN'T RECEIVE A RESPONSE AND DISCUSSED THE POSSIBILITY THAT HE HAD SAID 'STANDARD' WITH THE ASSIGNED ALTITUDE. WE RESET OUR ALTIMETERS TO STANDARD AND CONTINUED ON THE APPROACH WITH NO FURTHER DISCUSSION WITH THE CONTROLLER ABOUT OUR ALTITUDE. I BELIEVE THAT WE MAY HAVE BEEN 100 METERS LOW FOR ABOUT 5 NM DUE TO THE CONFUSION ABOUT THE CONTROLLER'S USAGE OF THE WORD STANDARD. I ALSO BELIEVE THAT WE WERE ALL A LITTLE FATIGUED DUE TO THE PREVIOUS DAY'S FLIGHT AND WERE ALSO GIVEN A DIFFERENT APPROACH AND RUNWAY AT THE AIRFIELD CLOSE TO THE DESCENT POINT; ALONG WITH THE ALTITUDE ASSIGNMENT. THIS CAUSED THE CREW TO FOCUS ON THE FMS CHANGES AND PULLING OUT DIFFERENT APPROACH PLATES WITHIN A SHORT DISTANCE FORM THE DESCENT POINT. THIS MAY HAVE DISTRACTED US ENOUGH TO MISUNDERSTAND THE CONTROLLER'S INSTRUCTIONS ON STANDARD/NONSTANDARD ALTIMETER SETTING FOR THE ASSIGNED ALTITUDE.