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.
When Ray Lewis got hurt last year Ellerbe filled in well enough that most thought he'd be an offseason priority for the Ravens, right up until he signed with Miami. The fact that Baltimore let Ellerbe go is telling. He's a prime "new toy" candidate, a player for whom expectations will be increased, if only because he swapped mailing addresses. There's a good shot that Ellerbe will be a decent IDP LB2, but let someone else chase the hope that he'll be more than that.