Amazon calculates a product’s star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers, and factors that establish reviewer trustworthiness.
The sizing is correct (lengthwise), but the wellies are so baggy around the ankles that I'm not sure they wont just fall off. I've decided to keep them however, because my grandson will grow out of them so quickly anyway. I will make a more informed purchase next time.