It’s a perspective issue. The rifle is on a raised platform/table/bed/whatever , and is much closer to the viewer than the box. The box is some distance below it, as you can see from the plastic wrap the view of which is partially cut off by the raised platform.
So the box, being much more distant from the viewer on the floor, looks too small relative to the nearby rifle.
If both were the same distance from the viewer the box would look big enough.
8~)