I found a solution myself. Actually two solutions. They can be found on the support page as Solution 11547560 ("Can Assura output the layout's lower-left and upper-right (X,Y) bounding box coordinates to a file?") and Solution 11572898 ("How do I output the XY coordinates of layout devices in Assura LVS?").
Second solution works fine for me. Short summary:
Put the additional option
to the avParameters block (or activate in the GUI).