How do I know if the car seat is properly leveled when rear-facing?

Check the level indicator on the car seat while the vehicle is on level ground — the ball must be completely in the blue zone. If the ball is in red, the car seat is NOT level and you must adjust the recline position. For infants 3 months and under, the ball must completely cover the light blue circle, and rolled towels may be placed under the car seat at the vehicle seat crease if needed. (Page 32, 36)