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 yellow marker shown in the image is not present. You get a total of six markers. I bought this specific pack for the yellow marker itself, as it is not available in the market, but got some other color instead. The quality of the unit I received is good. I advice the seller to update the image.