My colleague Ken Otten from my professional organization TRASA just sent an email that explains where the space that a wheel chair requires to transfer onto the bench provided must be located. 

The Access Board put out a publication in 2002 about locker rooms/dressing rooms and here is what it says:

Dressing, Fitting, or Locker Rooms

• If they are in a cluster, 5 percent, or at least one must be accessible.
• There must be an accessible route through the door and to all elements required to be accessible in the room.
• Operating mechanisms provided on accessible lockers must also meet ADAAG provisions for their operation and height.

These rules also apply to dressing rooms in retail shops

Lockers

If lockers are provided, at least 5 percent, but not less than one of each type (full, half, quarter, etc.) must be accessible. Accessible benches should be located adjacent to the accessible lockers.

Notice that the figure shows the clear floor space (CFS or the wheel chair space) perpendicular to the bench and the wall where the long side is located.  The 30X48 CFS is to be located along the short side of the bench, not in front of it, and positioned so that a person in a wheelchair can transfer directly onto one end of the bench.  Even though this only shows the bench next to the lockers, it also applies to dressing room benches that are inside a retail shop.