The department shall classify each inmate as soon as practicable on the inmate’s arrival at the institutional division and, subject to the requirements of Section 498.005, shall reclassify the inmate as circumstances warrant. Each inmate must be classified according to the inmate’s conduct, obedience, and industry. The department shall maintain a record on each inmate showing each classification and reclassification of the inmate with the date and reason for each classification or reclassification. The department may classify each inmate on the inmate’s arrival at the institutional division in a time-earning category that does not allow the inmate to earn more than 30 days’ good conduct time for each 30 days actually served.