Your order status will not change till 11/3/17 when you are asleep. I did the iUP in store pick up for the 8 Plus and the order status remained the same throughout the week and then changed to "Ready for Pick up" on the day of the launch early morning before store even opens.
You can go at any time of day. The check in time is just to keep the traffic flow go smoothly. But you can go early in the morning or later in the afternoon.