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 first time I bought these they were great and the dimensions were what the listing said they were. The second time though, the color of the envelopes was a lot lighter and they were almost 1/2" smaller on all sides. Not ordering again because its not consistent.