about compute vacf

Always include the list.

This isn’t a LAMMPS question. The documentation explains the dimensions reported. This is very fundamental stuff that you’re going to have to pick up on your own, or hopefully from the people teaching you.

https://en.wikipedia.org/wiki/Nondimensionalization

https://en.wikipedia.org/wiki/Normalization_(statistics)

https://en.wikipedia.org/wiki/Normalizing_constant