Well, it's possible they want it to just be held to the belt to prevent slippage along the belt, that would be function three here
http://www.carseat.org/Technical/tech_update.htm#Lock-off
(1) prevent movement of the belt relative to the latchplate, (2) maintain an applied tension on the belt from the floor anchorage through the latchplate to the lock-off, and
(3) prevent movement of the CR relative to the belt webbing. If performing function (1), the lock-off replaces a locking clip. If performing function (2), it does not replace a locking clip but eliminates the need for one. It is still useful to lock the switchable retractor, if this feature is available.
Function (3) is intended to improve ride-down and pre-crash stability by keeping the CR from sliding relative to the lap portion of the belt, but this lock-off usage does not fix the lap belt length or maintain belt tension. Function (3) does not replace a locking clip or the lockability feature of the vehicle belt.