Hi there,

Can you try to restart the Launcher a few times? This can cause the client to re-calibrate and may skip this download.

Otherwise, you can try going to your World of Warcraft folder and run the repair program, then run the Launcher again and see what happens.

If this still persists, you may need to let this download finish, as the Launcher checks the client for data corruption, and this may just be the client fixing itself.