Analog velocimeter decompensation with regul

I would like to know what can be done to correct decompensation between the speed regulator and the analog speedometer, (they do not mark the same, difference between 10-15 km). My vehicle is a 2007 DCI lagoon.

Hello everyone, hair is this decompensation that you have noticed has always been given or is it a new event in your car? Do you have tires and tires in original measure? Do you have any witnesses on the panel on when you drive your car and use automatic speed control, the car is faster or slower than the speed slogan, is it automatic or mechanical? Forgive so many questions, but it is intention to help you. kind regards .