Would you happen to be referring to the "Check Out Everything" and "Check In Everything" options in Axure RP's Team menu? The Check Out Everything option here will perform a check out of all of the team project's pages and assets (essentially everything that has the ability to be checked out), while the standard method of checking out only does for a specific item. Similarly, the Check In Everything option will perform a check in of all of the items you currently have checked out.
These options for checking in and out will follow the same rules as checking items in/out individually, so if an item or multiple items have already been checked out, a prompt will appear.
I hope this helps clarify some things!