What software did you install? WD Sync or WD Smartware? One is for syncing and one is for backing up. Each software performs a slightly different function.
There are numerous past discussions on WD Sync filling one’s My Cloud to capacity. There are various discussions on how to resolve the issue. One can use the forum search feature, magnifying glass icon upper right. Here is one past discussion on the WD Sync issue and possible methods of recovering the lost space.
