Blackstone was specific in their memo few years ago that their VOA will not be as precise as UOA. Reason is that there are much more UOA requests, so their methodology is focused on that.Those are not depletion values but just error rate between two sample points. Many people have posted VOA's where they sampled twice and the numbers were off by many ppm's. This is why VOA's and UOA's are to be taken with a grain of salt.