Odd Geometry Problem

I was working on a problem on Khan Academy, and it was talking about how a person was making soup in a pot that had a diameter of 30 cm. But the soup only reaches 25 cm. They want to store the soup in cube containers with edges that are 7 cm. The problem then asked me to solve for the number of whole cubes formed after storing the soup?

For some reason, when I used the equation for the volume of the cylinder that it gave me when I used the help option provided. The answer was completely different from the one I got. No matter how many times I tried to solve it, I could not get the same answer. 

Is there any way that someone can help me with this?