RCW 9.95.070 provides that every convicted person who has a favorable record of conduct and who performs the work, duties, and tasks assigned to him to the satisfaction of the superintendent and in whose behalf the superintendent files a report certifying that his conduct and work have been meritorious and recommending allowance of time credits to him shall, upon but not until, the adoption of such recommendation by the board, be allowed time credits from the term of imprisonment fixed by the board. The board will consider granting of good time credits only when certification is received from the superintendent. In every case there shall be a report filed, either certifying good time credits or denying them. This report shall set forth the reasons for the action taken.