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.
I used the smaller bottle throat gargle of the same brand that required diluting with water before gargling in the past. This doesn't need diluting, so you use up faster. But the bottle is larger. If I am going travelling I'll take the smaller bottle that requires diluting, but at home, if the price is right this does the exact same job.