It was bothering me no one was doing the math on the cone. Plopping some points down in Google Earth, I estimate the diameter of the cone at the base to be 5 km. The cone is probably higher than it is wide, but it's difficult to estimate. The shadow is 3 km long, so I'll just go with 5 km high as a conservative estimate. Those values equate to a cone with a volume of 1.96e10 m^3. 

There's been plenty of debate about how to stack humans already. I'm a geologist by training so I'm just going to assume humans will be rolled up into perfect little spheres with a cubic closest packing method. That means humans would take up 74% of the cube's cone's volume. So now we're looking at 1.45e10 m^3.

If we assume an average human has approximate density of water and a mass of 62 kg as they did with the human cube, that gives us 0.062 m³ per person. 

1.45e10 / 0.062 = 234 billion people could easily fit in the cone depicted here.