Number of units reported killed is wrong when unreachable units were on the tile.
this bug is in unittools.c line 2283:
The solution to this bug is easy. Everywhere else we check TWO conditions, e.g. line 2313
But on line 2283 we only check if pplayers_at_war and not if the unit is reachable.
Not surprisingly then, any unreachable units on the tile get counted as killed when it is reported "You killed the whatever and x other units".
x is wrongly inflated by exactly how many unreachable units were on that tile.