What are the weight and height limits for rear-facing mode?

In rear-facing mode, children must weigh between 1.8–22.6 kg (4–50 lbs) and measure between 43–122 cm (17–48 in). The top of the child's head must be at least 2.5 cm (1 in) below the top of the car seat headrest or shell, and harness straps must be at or just below the child's shoulders. If your child exceeds any of these requirements and is less than 2 years old, you must discontinue use of this car seat. (Page 10)