In calculating the community supervision percentage, the department shall:
(1) determine the county or county zone in which an offender is supervised by identifying the location of the offender's primary offense;
(2) have sole discretion in identifying the offender's primary offense under Subsection (1), taking into account the severity of the crimes for which the offender has been convicted and sentenced; and
(3) only include an offender on probation or parole supervision with the department in the community supervision percentage calculation.