It's almost certainly connected via some ERC to the channels in the body (most likely with linkParam) as a workaround for older versions of Poser not saving (some) channel values on the Body actor (ApolloMax uses a similar mechanism).

The P8 parameters panel shows both the dial value and the total value after ERC, but for older versions of Poser any ERC contribution to a channel value is invisible to both the UI and Python.