If you paid for 4 nights, you should get credit for 4 nights (regardless of the arrival and departure dates on your receipt)
It is that simple.
Call Guest Assitance and open up a file (not complaining), but just asking that you get rewarded as a 4 night stay, so you get your hilton honor's points. The hotel will either remove the first night's charge or (much more difficult), convince hilton honor's to give you the points your deserve.