I think you'll find that most stated capacities on things have a factor of safety built in. Would you use a ladder with a 200 lbs capacity if you were 199 lbs and the ladder were to collapse right at the 200 lbs mark? Probably not. The number they put on there is the safe range for use. If you go over that, you are doing so at a risk to yourself, even though you know the ladder can probably hold 250 lbs without a problem.
The lights are similiar. They have likely tested many stings, come up with a statistical value for how much current is used, added onto that a factor of safety, and put that value on the box. If you determine that it is using less, based on your own calculations or measurments, you are doing so at your own risk. Not something recommended by the manufacturer or anyone on this site I am sure.