ok ... so 840 grams in 4x2?
No, more like 896g or 32oz/2lb. Staggered grow - which meant harvesting half a side at a time. That's always going to produce more yield for the same amount of space as you have the staggered lighting (see below: one frame overhead, one frame side-lighting) reaching most of the canopy from top to bottom as one side grows ahead of the other. Then you cut the first side and do it all again.
This was one side of the tent that produced 20oz.There are three haze-type plants in there that produced 7oz, 7oz, 6oz. This is them at about 9 weeks and they went for another 3-4 weeks after that.