I got 3 of the sweatshirt rompers and absolutely love them.
I purchased the 0-6 month and it is huge. It fit my sisters 15 month old baby who is 22lbs.
Customer service says it doesn’t matter.
I got my daughter a few fall outfits. She currently fits in 12 month clothes. I ordered 12-18 months. I swear they're the size of a 2T or larger...HUGE. So maybe next year she can rock the pumpkin outfits. But very good quality and SUPER cute.