Strength of schedule is calculated from the opponents projected fantasy points allowed for the QB 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.
Jeff had his moments, playing for Tampa Bay, and played well in relief of Donovan McNabb for Philly before that. But his glory days as a Pro Bowl quarterback were 6+ years ago in San Francisco. He doesn't appear to be a great fit for what Oakland prefers to do on offense but as NFL backups go, and has done nothing in the preseason to make it appear as though JaMarcus Russell's job is in jeopardy.