Isn't it true that on the big car seats they measure height from the seat to the head, so total height doesn't matter basically? Is that the same on infant car seats? megans goes to 32" so as long as she is less than 32 inches and less than 30 lbs she can still be in her seat?

You have the Graco Safe Seat. :) Total height does count, but that doesn't take into consideration torso length. All kids are different. In a rear facing seat, even if the child hasn't outgrown the height/weight limits, if there is less than 1" of hard plastic seat shell above the baby's head, the seat has been outgrown.

Forward facing: If the child's shoulders are above the top harness slots the seat has been outgrown even if he/she is still under the height/weight limits.

Does that help?

Yes, thanks!

Seated Shoulder Height 10.5 - 16 inches

so if the seat says this how do I measure the baby to see if she'll fit?

That would be the torso length, from crotch to top of shoulders. It's best to actually try the baby in the seat, but that's not always possible.

Another issue that sometimes arises with newborns/small infants - When rear facing the shoulder straps need to be at or below the shoulders. If the straps are above the shoulders, even in the lowest harness slots, the car seat is too big for the baby.

I have a marathon for Madeline but I swear she's never going to fit in it. I haven't even bothered to try yety

She will eventually, but you're right, it's most likely too big for her now. LOL!

yeah, they sucked me in with a 5lb weight min and a great sale. I just love the seat, can't wait to use. I even considered putting Logan in it for a while but mariposa isn't really a boyish print...LOL