The device viewer shows an overview of the loaded content and additional media information, based on the selected node item in the device tree.
Only devices displayed in the device tree are shown in the device tab (no hidden devices).
In the top left corner you will see the media size, in the top right corner the frame rate for videos is shown. On the bottom of the thumbnail the clip container length is displayed. Below the thumbnail you see the media´s name, its DMX file and folder ID and the current opacity value. The last entry at the bottom shows the asset's countdown (when it is stored to the timeline).
Click on a layer field here in the device viewer in order to select the layer in the Device Tree.