I've played it many times. It's an incredible golf course that sits out on the end of Kiawah Island. One side of the course is on the Ocean Beach and the other side is low country marsh. The routing is a figure "8" with each nine ending along the ocean...but the back nine's final 5 holes are more dramatic and closer to the sea.
I believe Garrigus played it from the tippy tips on every hole (7800-7900 yards). The PGA will have the course playing shorter though and use different tees on different days. If there is any wind it'll play ~7500 yards. The fairways are actually pretty wide, what makes the course hard are small, undulating, and elevated greens that are like tabletops. When there is wind those targets get much smaller.
I would bet the winning score is closer to -4.
(Remember...they said the same thing about an over par winning total for the PGA's at Kohler...but they never use the back tees and the wind never blew).