Most of the perks on the Smithing skill tree seem to unlock new material/construction types that can be crafted. The description is always along the lines of:
Can create <material> armor and weapons at forges, and improve them twice as much.
As far as I can tell I can still only perform a single upgrade of these items at the grindstone or smithing bench, and many items still only improve in damage or protection by 1.
So what does "improve them twice as much" mean in this context?