Extreme Data Usage on Metered Connection

[Zyneste]

Also! Mine shows ffxivlauncher.exe and yours shows ffxiv_dx11.exe. Could that have something to do with it?

The launcher is the launcher/updater. FFXIV_ DX11.exe is the game.

Your overcap on data was for sure from downloading the game. I'd say your meter connection was monitoring the wrong connection or you had accidently still been connected. If you were tethering, check your tethering device for its data usage and not the PC itself.