its very easy to adjust your milage. lets imagine this is an example of your milage 123456.7, and you want to reduce it by 2k to make it 121456.7
remove the instrument panel and its cover to reveal the odometer as much as possible. you need to slot a small scalpel blade inbetween the 3 and 4. then push it towards the 1, now you can rotate the 1,2&3 together by 2 clicks. keep pressure on the blade to ensure these 3 digits are disengaged from the mechanism. it does not require a lot of force, however it needs enough to seperate the cogs and keep them clear while you rotate the digits.
the reading will then be 901456.7. now you need to remove the blade and insert it between the 0 and 1. push the blade towards the 9 and then rotate the 9&0 up 2 clicks. the milage would then read 121456.7, 2000 less than it originally did.
a good tip, do not start to adjust the milage unless you have all the numbers lined to to start off with, then you know that if you have them all lined up again afterwards that they are in the correct position. its easy to tell if someone has clocked the milage badly, so always start with a stright line of digits and end with one. you may need to drive a few miles to get them all lined up in preparaiton for clocking it.