Into the Story's cost reduction can only reduce its cost by {3}. It doesn't reduce the cost further if more than one opponent has seven cards in their graveyard or if an opponent has fourteen cards in their graveyard.

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Into the Story). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.