The first time that the daily incremental backup runs, it will back up all of the artifacts that are currently contained within an Artifactory instance. The next time that it runs (24 hours later), it will back up only changed or newly added artifacts, and add these to the full backup from the first run. So, what you’ll have is a backup of all of your artifacts up to the time that the last incremental backup ran. When restoring from a daily backup (incremental or not), all of the artifacts that were stored will be restored.
The weekly backup, by default, will run once a week and will back up all of your artifacts at that time. This backup can also be configured as incremental.