Why is my sizing for objects different from the tutorial?

I’m having trouble figuring this out… I will try to explain it as thoroughly as possible. So lets say a 5x5x.2 is shape A. That is for me. Now, in the tutorial, it says that a 500x500x20 shape is shape A. Why is the sizing doing that? Did they change the values or is there something that I’m doing wrong?

Screenshot - 6f1f26db785e43352c878bf7f1cc3356 - Gyazo Tutorial
Screenshot - d0bd9fbc724bfab0484ccdf3e0628a20 - Gyazo Me

The tutorial you are referencing is using a Box BSP Brush, where as you are using a Cube mesh. The Box BSP brush size can be set directly through the box settings or having its volume edited whereas the Cube mesh is already a fixed size and can only be scaled.