Nothing will be deleted. The backup size will grow with each change.
Over time backups will be deleted automatically. There will remain one backup for each of the last 7 days, each of the last 4 weeks, each of the last 12 months. There will always be at least one remaining backup.
Enter a retention strategy manually. Placeholders are D/W/Y for days/weeks/years and U for unlimited. The syntax is: 7D:1D,4W:1W,36M:1M. This example keeps one backup for each of the next 7 days, one for each of the next 4 weeks, and one for each of the next 36 months. This can also be written as 1W:1D,1M:1W,3Y:1M.
Once there are more backups than the specified number, the oldest backups are deleted.
If at least one newer backup is found, all backups older than this date are deleted.