Incorrect Grade VII Materia Stats

[Lumis_Arvalo]

Materia V - +12 Stat, can be overmelded past the first overmeld slot.
Materia VI - +40 Stat, cannot be overmelded past the first overmeld slot.

Materia VII - +20 Stat, can be overmelded past the first overmeld slot.
Materia VIII - +60 Stat, cannot be overmelded past the first overmeld slot.

Hopefully this illustrates that VII replaces V and VIII replaces VI.

This is correct. Yes, it looks weird because of the stat differential, but that seems to be the intentional design of it. VIII goes into the guaranteed and first overmeld slot, VII goes into the remaining overmeld slots because VI cannot.