Delete the currently highlighted/displayed ARO, layer, revision, or payment. If you delete an ARO, all associated layers, revisions, and payments are deleted. If you delete a layer, all associate revisions are deleted. If there are multiple revisions for a layer, you may delete the first, which means the entire layer is deleted, or you may delete the last, which restores the layer to its prior status. You may not directly delete a revision that is neither the first nor last, as that would cause inconsistent results. However, you may delete the last revision multiple times (4th, then 3rd, etc.).