Backup size changed after downloading from capacity tier

[Nas]

I have a request from user to download all backups from capacity tier back to performance tier.

What I noticed before starting in Backups>Capacity Tier> shows the Backup Size as 7.12 TB (3.29 actual).

After finished downloaded, I checked the size in Backups>Disk> shows the Backup Size as 6.79 TB.

Is this behavior expected, that same backup set on disk will consume more space than it originally did on object storage?