What is the proper harness strap height for rear-facing use?

When using the car seat rear-facing, the harness straps must be at or just below the top of the child's shoulders. The top of the child's head must be at least 1 inch (2.5 cm) below the red headrest/harness adjustment handle. To adjust harness height, squeeze the red adjustment handle and move the headrest to the proper position. (Pages 5, 34)