Strength of schedule is calculated from the opponents projected fantasy points allowed for the LB 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.
Harris actually had one of the better seasons of his career last year. His 123 total tackles were the second-highest total in his six NFL seasons, and he notched his highest number of solos since 2009. However, those numbers barely got Harris into the top 30 at his position in Fantasy Sharks Default IDP Scoring, and he'll be sliding over to SILB in 2013, so Harris shouldn't be looked at as more than a so-so IDP LB3 for the upcoming season.