Create custom attribute to device and add it in a calculated attribute function

Hello good Morning. It is possible to create a custom attribute to a device and add it in a calculated attribute function.

That is: I register an attribute called kmInitial on the device with value 2350

In calculated attribute I create one that works as follows:
totalDistance? (totalDistance - kmInitial): null

I think it should be possible.

Should I activate some function in traccar.xml or with that logic would it work?

You have to enable "processing.computedAttributes.deviceAttributes" in the config file.

Ok thanks you. It working