OP, I took the time to try to duplicate what you are seeing. Indeed, it does seem that NO credit is given for the "free" night as it shows the exact same nightly rate multiplied by five to give the exact same total rate. Contrary to what travelinfoo is telling you, this does NOT seem to be a situation of the four nights being inflated at a rate equal to or higher than the cost of the five nights without the promotion. I would suggest contacting either the property or Hilton Reservations to inquire further.