graco transitions booster

Hey parents ! So my husband recently purchased the graco transitions 3 in 1 booster seat for our daughter who is 16 months old, when we purchased it I told my husband I think our daughter is too small for that seat and we shouldn't purchase it seeing as how we can't return it (bought at babies r us) so anyway I was curious if other parents have this car seat and how old were the kids when they started using it, he thinks she will be ready for it in 2 months but I highly doubt it