Head Blacksmith Ferris:
Oh, you selected a Wind Stone! This practice is going to be on Wind!
Grant an attribute to the practice weapon that I gave you. I gave you spare ones to prepare in case of failure. If you're unlucky and fail even though you used all the Practice Attribute Stones, you'll have to buy Attribute Stones to complete the mission.
You can use other Attribute Stones that you already had or you can grant the attribute to other equipment. As long as you experience the attribute, anything goes.