On the first reading I thought that was the entire point. That they would have to deduce whether they where seeing the same statues from either side. Which by the end of the reading ofcause makes no sense since they don’t have and can’t pass information about that at all.

> Out of your friend’s window, which overlooks the opposite side of the graveyard, she can see eight.

It could be clearer, but it is in the description that your friend is looking in a different direction to you and so presumably at different statues.

It's not made explicit but I think there is not supposed to be any overlap between the visible statues. Otherwise I'm pretty sure the problem would become impossible.

  > Out of your friend’s window, which overlooks
  > the opposite side of the graveyard

I'd say it is pretty explicit, unless the same statues happen to be on the opposite side, which sound funny.

Count the shadows during the day.

I took this statement:

'The caretaker tells you each, individually, that together you can see either 18 or 20 statues. '

as being:

    size(see_A) + size(see_B) = 18 or 20

as opposed to:

    size(see_A union see_B) = 18 or 20

i would have assumed they would add the word distinct if they wanted to not double count overlapping statues.