Game will not let me temper my amulets. I click the first tempering category and when I click the second it unchecks the first. Go to redo first and it unchecks the other one preventing me from selecting temper. Tried this with 4 amulets always the same.
You pick the first temper recipe and let the blacksmith temper it. That way you get one of the stats included in the temper recipe.
Then you pick the second recipe and let the blacksmith temper it again. That way you get another stat tempered on it.
You can retemper your item within the same categories that you picked as long as you have temper charges left. With a scroll of restoration you can reset the temper charges but only once per item.