Quoting: Leafsfan98
Can you explain (however you want) then? I am not good with this side of the NHL
The quick and dirty explanation is that the cap is calculated on a daily basis, and if you aren't using LTIR and are under the cap, you "accrue" cap space based on every day you are under the cap - since the cap is calculated daily, it pro-rates out as you get deeper into the season. Since the deadline happens about 75% of the way through the season, teams only have to account for the remaining 25% of a player's contract - for example, if you have $1M in cap space available on the deadline, you would be able to fit a player with a $4M AAV under your cap without any issues, since 3/4 of his cap hit has already been paid out.
When teams are using the LTIR exception, the amount *doesn't* change - since LTIR is an allowance to go above the cap, teams only use it when they need it (and they will typically spend as close to the cap as possible before putting a player on LTIR, to maximize the amount of the exception.)
It's a couple years old so the cap numbers are different, but this is a pretty good
explanation that goes a little more in-depth.