Hi Vincente,
thank you for your answer.
Actually I'm using this evaluation board to program the microcontroller:
https://www.nxp.com/products/processors-and-microcontrollers/additional-processors-and-mcus/8-16-bit...
I've already tried to modify the parameter in debug configuration but it has anyway an higher clock. I can understand it because the answer in the UART port is faster than 9600kbps (as setted). It seems almost 5% higher.
In parallel I've tried to use the USBDM interface with its software. With its clock trimming setup it works!

So, what I would like to know is:
-why the evaluation board can't set the correct clock frequency?
-Is in your opinion the USBDM interface reliable for programming? Also for production? I'm asking this because it seems that it's an open source hardware and software.
Thank you for your attention and best regards,
Mattia