Wrong star ratings showing on page

Hello,

Even though customers have given us 5 star ratings, it shows as 4 star in each review, though the calculation for all reviews is correct. This is happening on all pages where reviews are enabled. For example in the page attached, all the customers have really given us 5 out of 5 stars, but next to each review it shows 4 out of 5 stars, but the aggregate calculation of all reviews is correct.

How could I fix this please?

The page I need help with: [log in to see the link]