So, let's the math again (and correctly this time). If the guys at the PCFG mining operation processed 16,300 yards, that's about 24,450 tons of gravel. If they got 63 oz. of gold out of 24,450 tons of gravel, that's about 0.003 oz/ton or about a tenth of a gram per ton. Mighty poor grade for a placer mine which is probably why are giving up.
As for that 0.279 oz/ton gold assay that EXTO reported recently, until they post a geological report to go with it, signed by a credible geologist or mining engineer, it should be considered a made-up number. And one assay is never enough to characterize an ore deposit. Legitimate mining companies end up with hundreds or thousands of assays before they can establish whether it is minable or not.