Mysterious off-board artillery losses

[jeffreywilens]

At the end of a game, the victory score screen reported that I had lost 5 "units" of artillery (or maybe that means 5 points of damage?) However, all of my artillery was off-map and all 4 batteries fired at what appears to be full strength the last turn.

Any explanation for this? I imagine there could be automatic off-board counter-battery fire but I think my opponent only had mortars which should not have been able to reach my heavy guns.