Confusion with AddForce with ForceMode.Acceleration

In the official documentation, the description for ForceMode.Acceleration is:

Add a continuous acceleration to the rigidbody, ignoring its mass.

Apply the acceleration in each FixedUpdate over a duration of time. In contrast to ForceMode.Force, Acceleration will move every rigidbody the same way regardless of differences in mass. This mode is useful if you just want to control the acceleration of an object directly. In this mode, the unit of the force parameter is applied to the rigidbody as distance/time^2.

However, I don’t know how long is that duration of time, or where I can set it.

Or is it that I am not understanding how this works correctly?

Thanks in advance!

There is a good explanation of how different ForceMode works here