From what I've heard there can be wording put into the contract that if on the 4th year the Chiefs cut Poe and they owe him 3 million that the Chiefs only have to pay the difference if he's picked up by a different team.
Say Poe is cut in year 4 but is picked up by team whoever for 2 million a year. If that wording is in there the Chiefs only owe Poe a million. If it isn't in there the Chiefs would owe Poe his 3 million and then team whoever would pay him 2 million. Kind of a big deal.
I've also heard that a 5th year option could be added but for the top 10 draft picks it's at a MUCH higher rate. Something like the top 10 of their position but for 11 and lower (which Poe is the 11th pick) it's something like the top third of their position. Not sure on the details but I know there are differences for where he was picked and the 5th year option pay.
Needless to say there are a LOT of stipulations that can be added, removed or modified. It's not quite as simple as saying here's a 4 yr, 11 million dollar contract now sign it.