When using solvate_box top build a solvation box, it creates a box of double the size specified. E.g.:

solvate_box 1.0 1.0 1.0

will create a box of size 2.0 x 2.0 x 2.0.

I do not know if this is a bug or a misunderstanding from my part. When I noticed a seemingly excessive number of water molecules, I started playing with boxes of water alone.

Intuition says the parameters to solvate_box should be the box dimensions, but it may be that they are rather like a 'radius', i. e. distance of the box sides from the center of the box.

Most probably the easiest fix for this behaviour would be to document it.