the details might be wrong, but the salary for toews is the normal ELC@850k plus around 2m in bonus money, which is included in the cap hit. these bonuses apply only to entry level contracts and maybe also bonuses added to contracts to 35+ year old players. keith was on a "normal" contract with no bonus clauses.
now it's possible to exceed the cap by the amount of the bonuses that can be paid out, by moving the bonus money to next year. there are i believe A and B bonuses, which are things like winning the scoring title or scoring 50+ goals and stuff like that and also bonus for winning awards such as the CS.
now that toews won the CS and the bonus is paid out, it will then be taken away from next years cap, where the bonuses were moved to comply with the cap this year. i hope this makes sense. details might be wrong, but that's the general idea of it.