I believe the bolt should sit even or lower than the board or it will poke a hole in the trunk mat. There is a recessed washer for the top of the board that reaches the stud.
The large toothed bendable for reach wingnut is rounded so it also doesn't poke through the mat. The wingnut under the board that holds the tire, jack base and hook is just a regular wingnut. So there is 2 wingnuts. One above the board which is adjustable by bending it for depth and one common wingnut below the board.