              The number of parameters refined in the least-squares process.\
               If possible this number should include some contribution from\
               the restrained parameters. The restrained parameters are\
               distinct from the constrained parameters (where one or more\
               parameters are linearly dependent on the refined value of\
               another). Least-squares restraints often depend on geometry or\
               energy considerations and this makes their direct contribution\
               to this number, and to the goodness-of-fit calculation,\
               difficult to assess.