"Torque it till it strips, then back off half a turn"

It's just a walmart bike. You can't hurt it that badly, and even if you do, it doesn't matter that much. More than likely all the other bolts and nuts on the bike are at the wrong torque, the bearings aren't greased or preloaded properly and the spokes are too loose. For the cost of having it assembled right, you might as well buy another bike.