(Inventory > Re-Stock > Smart Calculate)
The 'Smart Calculate' method when creating a PO isn't in fact 'smart' as it only gives the average number from the previous PO orders.
What would be 'smart' would be if it took the SKU daily consumption rate and the supplier lead time to calculate the minimum stock you will need between re-supply orders.
What you have currently is more like "lazy calculate" as its just a way to not need to remember what you last ordered.
Does seem like an obvious missed opportunity for a great feature, no?