Local seeding issue

Hey guys, I found another topic on this but I havent been able to resolve the issue yet.

Heres the scenario: (and its the same for all my clients)

I run all my clients backup to my backup server - Once a month I attended site to perform a full backup - I then bring said full backup to to server, plug it into USB on server and then want to use this FULL backup on the urbackup server so that I do not have to run that full backup over the internet.

So what I read in other topics is to just run a backup of the folder that contains all the data at my client, I dont need to keep file paths or anything? so I just install a client on my urbackup server, run a full backup of of the folder (do I install the urbackup client for that client, or can I just add a new site and install the client for the new site?) once I have run that full backup.
I can then go run an incremental backup on this client in urbackup and it should detect all the files and the backup should be quick.

But for me if I do it in this process, the incremental backup takes 4 / 5 or maybe even more days because it says its still backing up say 500gb over the internet, so its as if the local seed hasnt worked.

Any advise would be welcomed.
thank you