I wouldn't assume dredges to operate at 50%, 12 tons/hours. They should operate at 100%, 25 tons/hours. Because remember, the original capacity is 50 tons/hours. Then John downgraded the capacity to a conservative 25 tons/hours.
They're samples. After a few tons of great results, the area may have low concentrations of gold. Or they could have an entire season of high grade deposits. We just don't know.
But samples indicate whether dredges should stay put or MOVED for better pastures.