Like other review boards, 90% of a review is visible to everyone. The "Private Details" section, however, is only visible to site contributors (those who have earned access by contributing reviews of their own). After your 3rd review, your account gets upgraded with Private Details access which gives you the ability to read all of the private remarks the reviewer has shared in the review.
This account upgrade lasts for a period of 4 weeks, and can be extended by an additional 4 weeks for every review that is written and approved by the site moderators.
If you allow your earned access to expire without extending it by writing reviews, your account will be downgraded to the basic account and will have to start the process over by submitting 3 reviews to be approved.
This what I found