ok so LTI space works on a basic level like this:
you dont gain LTI space or relief unless you EXCEED the salary cap (this year 70.2million) therefore in order to take advantage of Kesler and Booths injury on opening day the canucks would like to be as CLOSE to 70.2 million as possible. So they will pick contracts that will add as closely to 70.2 million as possible.
math model: team salary of 65million
salary cap of 70.2
player injury of 4million
replacement player 1.2million
salary cap savings 0$, why they didnt spend to the cap
team salary 70.2million
player injuries 9.2million (5kes 4.2booth)
replacement players (kass ebbett 2million approx)
salary cap LTI usage FULL 2million. canucks were at 100% of the cap therefore whatever players they add are full value LTI replacements.
this is a very basic understanding of it, i dont even know if the formulas have changed in the new CBA, but this should give you a basic idea
edit: forgot there is also the issues of schroeders performance bonuses on his contract. under the new CBA these might be applied to next years cap instead of this years which further muddy the waters. (really not sure on this would need gilman to confirm its very complicated)