this is what the manual says:
1. Using the shutter actuation counter.
Your camera is provided with a 3-digit shutter actuation counter in the bottom which will tell you how many times the shutter has been used so that you will know when the camera will need maintenance. It counts 10 shutter actuations as 1: that is, if it shows 150. the shutter has been actuated 1,500 times. after reaching 999 ( 9,990 shots) it will return to 000 with ten more shots.