Strength of schedule is calculated from the opponents projected fantasy points allowed for the DL 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.
In 2011 Carter racked up 10 sacks and was a top 20 defensive lineman, but he was injured late in the year and cut loose by the New England Patriots that offseason. Carter then moved to Oakland, where he a complete non-factor last year in his first season with the Raiders. There's a modicum of upside with Carter as a starter in Oakland given his two top-20 IDP finishes since 2009, but at 34 years old it's far from certain that Carter will ever sniff that level of production again.