Amazon calculates a product’s star ratings using a machine learned model instead of a raw data average. The machine learned model takes into account factors including: the age of a review, helpfulness votes by customers and whether the reviews are from verified purchases.
Ordered a size bigger, as suggested, and they are still far too small. Contacted the company directly as requested on their packaging and apparently they can't do anything about it as I am an overseas customer (Australia). Very disappointing as now I am stuck with a pair of slippers that cannot be worn and will cost more than the purchase price to return.