Product: 
ccc6

CCC always examines the files on the destination to determine if they already match those on the source. If you have a volume that is virtually identical to your source, CCC will copy only the items that are different between the two volumes.

Scenario 1: Backup created by a cloning utility

If the software you used previously created a non-proprietary copy of your source to the destination, then CCC will copy only the items that have changed since you created the backup. CCC doesn't care what application you used to copy the files previously, only whether the files match based on name, path, and modification date.

Scenario 2: I replaced my hard drive with an SSD, and now I want to use the HDD as my backup

Whether you copied your HDD to the SSD or used Migration Assistant to get your data there, the bulk of the data on your HDD and SSD are identical. Once again, CCC doesn't care how the data got there or what application put it there, CCC will copy only the items that are different between the two volumes.