Add up the numbers there. It's the "uncertainty" part of the equation.
I'm sorry, but 538's model makes no sense.
I was going to make a long post today on why his model sucks...but the above image goes far beyond what I know is wrong with his model.
The above is nonsensical. Nate's reputation is going to take a massive hit on the 9th.
Also the model works by simulating 10 thousand runs of the election. That poll probably barely moved the numbers at all and the slight drop is due to deviation in the simulation. Really he should be running 100 thousand or more sims I think.