The Dimensions of a physical space determine its physical volume.
The volume of space within a cube is the product of its dimensions of length, breadth and height. This is a physical measurement of physical space, which is the absence of physical matter or the space that physical matter takes up.
Dimensions of Reality are determined by the vibrations of energy that are creating the reality.
Vibrations of energy are the product of their frequency and wavelength.
Frequency determines Time and wavelength determines Space.
A change in frequency and/or wavelength changes the vibration of energy and changes the reality which that energy is creating.
As the frequency or wavelength of a musical note changes, it becomes a different experience and we experience the sound in a different way.
As the frequency or wavelength of my reality changes, it also becomes a different experience and I experience reality in a different way.
The existence of many different dimensions of reality allows each of us to either create our own reality or enjoy the same reality as others.
My personal reality is the product of my personal time and my personal space.