We just drilled through the wall twice in the last month- but since it wasn't me doing the drilling, I could be wrong. It could be 1/8" or 1/4" on the outside as well.
Our sticker for our washer dryer hole was also WAY off. We did our research on the other hole and checked at night to ensure where the framing was.
The key is, check for the solid sound of the backer board, or call heartland for sure. And don't be too upset if you drill and need to redo because the sticker is in the wrong place. 😜