Edited Jan. 29, 2019 at 8:33 p.m.
On the main page the projected cap space is what the expected cap room will be at the end of the year if the current roster (including injury reserves, call ups etc) does not change from now until the end of the year. It does not take into account current year performance bonuses. The projected cap space of 4 million includes Horton's 5.4 million cap hit.
The current cap space is how much cap (entire year cap of a player) they can add and meet the cap requirement at the end of the year. This cap room does not include potential LTIR reserves. So the leafs current cap space of 11 million does not included Horton's 5.4 million cap hit.
For the record Horton is on the LTIR but by the rules of the CBA is that CAP relief can not take place until there is no CAP room left. re: Horton's CAP hit must use CAP room up first if there is any left so that's why currently his cap hit is being treated as IR rules rather than LTIR rules. It comes down to the programming of this site,
So the order of using CAP room is. Active and IR players first, then LTIR players only up to no CAP room left (Any extra unused LTIR player cap becomes the reserve), and then if room left performance bonus. If there is not enough room for performance bonus then it gets carried over to next years cap.
So using the projected cap space at the end of the season of 4 mil which Horton's cap hit is already included they can pay up to 4 mil in performance bonuses without any carryover.