This is something we saw with a number of early partners. In the app manifest, in the Application UI section of Visual Studio’s editor, there’s an option called Show name with a variety of options:
By default, this is set to “All logos” meaning that the value in the “Display name” field (also on the Application UI section), or the value in the “Short name” field, if given, will appear on the lower left of a tile as shown here:
As you can see here, the display name/short name text is redundant with the app name that’s already on the tile. To remove it, select one of the other options in the Show name drop-down.
It’s a good thing to double-check before submitting an app to the Store. Having a name show on a tile when the graphic shows a name too won’t cause the app to fail certification, but it does look a little silly.