Clean install and restore from CCC

Bill I assume you have done subsequent backups to the first backup drive so the Safety Net which I imagine you have turned on (it's on by default) will have created Original State archives. These are records of how things were before each backup.
If you open your original backup drive you will see a folder called Safety Net, open that and you will see dated folders which represent the changes at each backup a little like Time machine. Also in this folder, usually at the top is a document called About this folder which gives a full explanation.
My guess is this folder will account for the difference in size.

Thanks Rod. Didn't change any defaults on CCC. I did not find the document 'About this folder', but Safety Net's size is 24.73 GB, so that explains the difference. I have done just one update (backup) to my original CCC drive since I did the original clone. Don't usually do much that needs backing up.
Checked my Mac HD and it shows 74.46 GB in use, more than my CCC drives. (I run TM on another ext HD). Not sure the difference on that but won't lose sleep over it. Thanks again to you and all who helped on this.