In summary, the development of the numbers for these nine patriarchs may have proceeded as follows: 1. A set of plausible numbers was invented. 2. Each lifespan except Enoch's was increased by 300 years. Enoch's lifespan was increased by only 100 years. 3. All the numbers were multiplied by 2.5 (or multiplied by 10 and divided by 4), and rounded down to whole numbers if necessary. It is not likely that one person performed all three steps with the final set of numbers in mind. If someone had begun with the requirement to invent 27 numbers within the desired range, he would probably have invented them in the final form. They might for convenience have all been multiples of 5 or 10, but it is highly improbable that they would have been reducible by fairly simple arithmetical operations to a set of plausible numbers. It is more likely that the final author or editor used an existing list that included numbers at stage 2, and multiplied them by 2.5 because this gave lifespans in the desired range. It remains an open question at what point the explicit lifespans became part of the set.