This measurement is as simple as possible, as along equator there are exactly 60° from Africa to South America. After billions of years of tectonic drift, this is a fact.
This can help us understanding the convection rolls system in general. And it can also teach us that nature behaves in a more complex way than we think at first. A linear thinking method makes us reason that the wideness of the ocean must be arbitrary. In nature, continuous movements are constantly subject to physics and show regularity and linear procedure at the same time. Understanding this, we can trace the tectonic drift backwards with more accuracy than before.
The Atlantic Ocean spans two of those cells (sections of convection rolls), as can be seen here were the layers of Earth are drawn to scale.