Strength of schedule is calculated from the opponents projected fantasy points allowed for the RB position. The best rating is +16 which gives the player the advantage against the defense and indicates an easy opponent, the worst rating is -16 which gives the defense the advantage and indicates a tough opponent.
Stephens-Howling is a special teams stud who figures to make the Steelers roster as a return specialist and occasional third down back. Expecting much more from the undersized vet would be setting your expectations too high.