If the actions taken pursuant to sections 5 and 6 do not reduce the county jail's population to the level prescribed in section 6(1) within 28 days of the declaration of the county jail overcrowding state of emergency, the original sentences, not including good time, of all prisoners sentenced to and housed in the county jail on that date shall be equally reduced by the sheriff by the least possible percentage reduction necessary, not to exceed 30%, to reduce the county jail's prisoner population to the level prescribed in section 6(1).