That's what I though as well. Would appreciate it if someone who knew for sure could chime in here. It certainly is a strange situation and makes all the projections about how we could fit Stamkos in under the cap a lot more complicated.
Before the season starts the Maple Leafs have to place Horton on Long Term Injured Reserve. When they do that the team continues to pay Horton AND his cap hit will remain on the books. However, if Toronto exceeds the cap ceiling than they can exceed it by Horton's price of $5.3 mil
For example, say the cap ceiling is $70 mil. The Leafs place Horton on LTIR and the following happens...
If the Leafs total cap is $64.6 mil (not including Horton) than their cap space would be viewed as $69.9 mil (teams $64.6 + Hortons $5.3mil) out of the $70 mil cap maximum.
However if the Leafs total cap hit is at $64.8 mil than their cap space would be viewed as $70.1 mil out of a $75.3 mil cap maximum. (Because you can exceed the limit by his salary)
The problems with it is that the Leafs are still losing money by paying him despite not playing, and the Leafs already have so much dead cap space elsewhere (Gunnarsson, Kessel, Gleason, Robidas).
Another issue with LTIR is that no matter how many people you have listed it does not remove all of their salaries if you go beyond the cap. For example, Robidas has been out all year just like Horton but if they are both on LTIR it DOES NOT mean the Leafs would have $8.3 mil available. Only Horton's would take effect and Robidas' contract is just dead space.