Hello Cristiano,
I am the pround and happy owner of a new button box that iRacer88 built for me, and as per discussion above, it incorporates the DLC247.
In SimDash I got RPM% to work by entering percentages multiplied by 100. For example, I enter 10% as "1000" %. You most likely have a division by 100 in your software that should be changed. This works in the LED area, however, in the gear area, SimDash accepts 90% entered as "90" %, which is correct.
I've attached an xml export to better explain what I did.
I hope this helps.
Alain