Pgbackrest info output interpretation

I am having confusion trying to understand the database size, backupsize and repo backup size..

In my DB server I have du output as follows.

/data/edb/as16
[root@db1 as16]# du -h -d 1
5.3G    ./data
25G     ./tablespace
30G     .
[root@db1 as16]#

On my Repo Server pgbackest info says .... 

full backup: 20251114-121504F
            timestamp start/stop: 2025-11-14 12:15:04+05:30 / 2025-11-14 12:20:58+05:30
            wal start/stop: 000000010000000500000024 / 000000010000000500000024
            database size: 3GB, database backup size: 3GB
            repo1: backup size: 431.0MB

Could someone shed some light on    431 MB and database size:3GB, database backup size : 3GB  compared to the DB cluster on disk usage output ?

How to correlate the pgbackrest ( info) database size, database backup size and repo1 backup size     and actual du output on DB cluster. 

Note: I am using zst compression on pgbackrest 

Regards,

Krishane