Avamar SQL incremental backup "synthesizes" to full - reported size discrepancies?

Working with a customer on various things and we are seeing something that I want to clarify.

Customer is doing a typical SQL daily full backup with periodic incrementals. The full backup shows the full DB size in the Activity Monitor and in the Restore tab. However, the Incremental is showing the log file size in the Activity Monitor but shows the full DB size in the Restore tab. The session log does mention that the incremental backup is being "synthesized" into a full backup, but there is an obvious discrepancy between the Activity Monitor value and the backup size.

Where this has caused difficulty is with the customer expectations in terms of replicating the SQL backups. They were expecting incremental backups in GB to be replicated, but instead they are seeing backups in TB replicated, and the replication time is much longer than they thought it would be.

So, I need to find something that actually discusses the value discrepancy that I can reference for them. I am also going to look at their replication configuration as they may be using AMS/NCR for the SQL replication, but as I understand it, that should theoretically make the replication faster for something like SQL with a high change rate and large backups.

Anyone else run into this situation? All comments/feedback appreciated - thanks.