How do I change the number of reviews displayed before the "Show more reviews" button?

Changing the number of reviews displayed before the "Show more reviews" button can be done by changing the "Reviews per page" field on the "Reviews widget" section of your Loox settings

Please note: This will only affect widgets on product pages. To limit the number of reviews shown on an aggregated reviews widget (on a dedicated page or on the homepage), see How do I show all reviews on one page?