Based on the screenshots, I get that this is not very clear. If you fill in a number on the backup settings screen, the corresponding text on the scheduled backup settings screen will clarify how this works.
But, to answer your question:
- Number of full backups on the backup settings screen: the maximum number of full backups that can be stored on the backup location (doesn't have to be the server itself)
- Number of full backups on the scheduled backup settings screen: the number of full backups you want to use. This can equal or lower than the number you entered on the backup settings screen.
i.e.:
If the maximum number of full backups on the backup settings screen is 4, the number of full backups on the scheduled backup settings screen should be 4 or less.