Duplicate larger than backup?

We run a backup job to deduplication. It's happy.

Byte count          : 587,820,528,941 bytes
Job rate            : 1,073.00 MB/Min (Byte count of all backup sets divided by Elapsed time for all backup sets)

Scanned byte count  : 517,123,320,832 bytes
Stored byte count   : 335,055,311,872 bytes
Deduplication ratio : 1.5:1

We then run a duplicate job to copy to USB. It's still going, but it's at 1.4TB and still going. Is that normal?