which side out wonderboard

Taking over shower walltile job where backer is installed. Some sheets rough out some smooth with label out. Wonderboard label says for "wall installations label side down or wet". This is a wall, what could that possibly mean, and how much does it matter?

The rough side gives the tile something to bite too, What size of tile is going back in? The bigger the tile the rougher you want it when taping your joints make sure to sand that down flat, but just hang it normally,