Would you like to adjust the speedometer of the new speedometer, how do you do that?

Hello, I’m looking here in so if you want to manipulate a guide for this. This should end up for any illegal reasons, but has the following background: I drive a Calibra built on XE with NE Tacho. But the NE Tacho has only the rev meter up to 7000 and the XE Tacho up to 8000. Now my car has 188 down and the other Tacho 257 and I want to adjust the stand to original. I was told by one I should simply dismantle the disc and with a screwdriver twist the numbers. The only thing that now grbachtr has to me is a scratching number and the fact that it can’t be turned. So how do I do it best to break it oghne still merh? And: when cih converts the tacho, how do I separate the tacho wave to be able to take the tacho?