Sorry I completely ignored our 2015 hit. Oops
For the years when the contract would actually be in effect, the hit is worked out as the difference between the average cap hit for the buyout and the actual amount the player would have earnt. As the last year of CoHos salary was to be the most, ie above the average for the contract, we actually get credit. The reaming four years are just the average cap hit of the buyout.
I think this is roughly right, anyway