That's the way Excel numbers it's columns, A-Z, then AA-AZ, BA-BZ, etc. If you understand hexadecimal, imagine that with A-Z instead of 0-F. English version doesn't number the zones, it just shows their names.

The last 3 zones according to datamining and google translations are:
-The Rimilala Trench Bottom (Le fond de la tranchée Rimilala)
-Stone Temple (Temple de pierre)
-Sunken Vault (Caveau englouti)