If determinist methods for estimating reserves are used, then reasonable certainty is intended to express a high degree of confidence that the quantities will be recovered. If probabilistic methods are used, there should be at least a 90% probability that the volumes actually recovered will equal or exceed the estimate. The SEC considers the concept of reasonable certainty to imply that, as more technical data becomes available, a positive, or upward, revision is much more likely than a negative, or downward revision