There are rumors swirling that the deal is oddly structured.
6 years, 90 million of it are guaranteed.
The last two years, and the other 46 million contained, are based on him reaching certain performance level bonuses.
I can't find a link to confirm it but I know there were a couple up that mentioned 6/90 as the contract. If true, I think the 6/90 method is much better for Chicago than a straight 8/136 deal... but that goes without saying.