Strength of Schedule is calculated from the opponents projected fantasy points allowed for the RB position. The easiest rating is 1 which gives the player the advantage against the defense and indicates an easy opponent, the most difficult rating is 10 which gives the defense the advantage and indicates a tough opponent.
Jackson is at the end of his great career. He has scored 12 touchdowns over the last two seasons but that goes along with just 1,350 total rushing yards and a 3.6 yards per carry average. Jackson could still contribute in a complementary role but he won't have much fantasy value.