This is the error page members of other membership levels will be redirected to.
For now, since you only have one membership level this page is not relevant, however, if you do choose to add extra membership levels in the future, this page will definitely be relevant.
When this page will be relevant, we also recommend adding a sales pitch to this error page to try and sell members of other membership levels other memberships / upgrade their membership.
This is the default content provided by the Wishlist Member plugin:
You do not have the correct privileges to access this content. Please upgrade your membership level in order to access this content.