I want to calculate the number of microstates in a system for, say, n indistinguishable particles in a 3D box. Some examples I see just represent one microstate as a list of positions. Other examples use a list of positions and a list of velocities (translational and rotational). And if you're supposed to use position and velocity, why not acceleration too? I can maybe see why you wouldn't use "jerk" and fifth derivatives of position and so on.