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.
The former number one pick has lost the battle to become the starter once again. His play was mediocre and moving on to another team might be the best option for Smith to try and jump start his career.