Suppose you have a new document and you expect 15 users to access this document, you will assign only 10 CALs to document and check the "Allow dynamic CAL allocation" without manually adding any user.
whenever a user access this document he will take one CAL automatically and will appear as if you have manually assigned this user, now when the number of CALs reach 10 and a new user try to access the document he will not be able to do so.
"Allow dynamic CAL" means that, instead of manually add any user to a license, you allow any user that logs into the system to get a license from the server.
"Allow dynamic CAL" - For small number of licenses, it's not usually a good idea, and assigning them manually doesn't take too long. However, when you have several dozens of licenses, you usually let the users access the system, get their licenses dynamically, otherwise it will take a lot of time to identify them and add them to their documents. Again, it depends on how you manage your systems.
No license will be deleted nor unassigned from any user, unless you do it manually. You have to allow 24 hours quarantine period between you want to delete an assignment and you actually delete it. For example, User 10 has a license and is no longer going to use it, so you cannot assign it again to another user until 24 hours later.
