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.
Delivered on 27th jan 2020, initially it was working very fine. Very fast charging. Built quality seems fine. But stopped working only after about 1 and half months. To be precise it stopped working on 17th March 2020. I think its better to put a little extra money and buy a reputed one.