The FittedBox lets the Text be any size it wants,
but after the Text tells its size to the FittedBox,
the FittedBox scales the Text until it fills all of
the available width.

Example 19

But what happens if you put the FittedBox inside of a
Center widget? The Center lets the FittedBox
be any size it wants, up to the screen size.

The FittedBox then sizes itself to the Text,
and lets the Text be any size it wants.
Since both FittedBox and the Text have the same size,
no scaling happens.

Example 20

However, what happens if FittedBox is inside of a Center
widget, but the Text is too large to fit the screen?

FittedBox tries to size itself to the Text,
but it can’t be bigger than the screen.
It then assumes the screen size,
and resizes Text so that it fits the screen, too.

Example 21