The level indicators can be anywhere between 30 - 45 degrees with most of them falling somewhere around the 40 degree mark.
If you look at the side of the carseat you will see a ridge/line that follows where the babies back is. You want that line to be 45 degrees from the ground.
If you are having trouble eyeballing the 45 degree angle, then take a piece of paper and fold it into a triangle. Match the ridge/line of the carseat up with the 45 degree angle of the paper and make sure the bottom of the paper is level with the ground.
You can lower the foot on the base to achieve a more reclined seat OR you can use up to 3 pool noodles taped together in a pyramid shape to get the right angle OR you can roll a towel up tightly to help achieve the right recline angle. If you use the pool noodles OR the towel, they would get placed under the base in the bight of the vehicle seat (where the vehicle seat back meets the vehicle seat bottom).
As the baby gets older and moves into a convertible seat, any angle between 30 - 45 degrees is fine (most like to be closer to 30 degrees), but right now you are correct with thinking that your baby *needs* that 45 degree angle.