Is the message “Sorry you are not allowed to go to this page” one that you have written, or are you using other plugins in combination with Restict User Access?
You can find the FAQ here: https://www.ads-software.com/plugins/restrict-user-access/faq/
Drip Content
With this option you can add a time to the conditions for the Access Level. This means that a user will get access to the content after the time has passed. It does not work for Levels that are synced with User Roles.
See screenshot: https://ps.w.org/restrict-user-access/assets/screenshot-2.png?rev=1490353
Negate
When you negate a group of conditions, it means that you restrict all other content but that. So if you add a condition group for All Posts and negate it, only users in this level will be able to see all content but posts (you effectively restrict everything except posts). Posts will be accessible to all users.
Exposure
This means whether your conditions should be applied to single posts, pages, custom post types, content written by select authors etc. (Singular exposure), or if it should be applied to the blog page, post type archives, author archives etc. (Archive exposure).
Let me know if this answers your question.