The whole odometer roll comes out when you release the black clip on the left.
Release the two tiny prongs of the clip using a blade screwdriver as wide as the clip.
The odometer roll removed with its original mileage. Note the prongs between the wheels line up.
Once you have the roll out, you just need to loosen the gear outwards a little by gently tapping the center pin using a small hammer. You do not need to take the gear off, in fact it is not advised. Just get the gear until the white plastic posts are free from the holes in the gear.
Once there is some space between the number wheels, you can rotate them to any number. Remember, the metal prongs between the wheels lock into the bar in back of the odometer wheel when installed, so they all need to be inline as shown in the photo.
Once you have the number you want, gently tap the the gear back onto the shaft in a circular motion around the shaft. You may want to put some scotch tape opposite the prongs to keep the numbers as you set them. Install the roll back into the odometer, making sure that one end of the prongslocks into the bar behind the odometer.
Place the black clip back on the left of the odometer. Remove the tape and you are done.