In a double deck game, the dealer accidentally shows you the bottom card as she holds out the deck for you to place the cut card. If it's a bad card, you insert so that card winds up near the bottom and out of play. You start the count at +1.
If it's a good card, you insert so that card winds up near the top of the deck and in play. But where do you start the count to take into account that "extra" good card which may or may not come to you?