With artboard selected, why is the layer edge bigger than the artboard when no layers are selected?

[NDL_DH]

There is nothing selected except the artboard, and I have layer edges turned on (View > Show > Layer Edges), and there's a layer edge around the artboard that's bigger than the artboard?

Even though the canvas and the artboard have the same dimensions 640 x 6000. 

So why is this happening and how can I find out what's causing it?

Notice the dark blue layer edge outline (can turn on under View > Show > Layer Edges).

[Bojan Živković]

Some of the elements is larger then artboard itself. That is possible, you can place or create object larger then canvas or artboard. Part of object that is outside of artboard dimensions will not be visible, you can move it and change what is visible if that layer is not locked. 

If you want to get rid of invisible, outside part of object use Select > All  then Image > Crop. You can crop pixels on layer that is not locked nor smart object layer.

[mglush]

If the layer is what is selected, denoted by the blue line, can you indicate where the edge of the canvas is? It is not clear to me in the screenshot. 

Michelle