It looks to me as though everything is working as expected. You took a full backup of your system, which was around 147GB - most of which is in a tablespace. It got compressed down to 20GB. You then took two incremental backups, which are by definition much smaller and take a short amount of time to run.
I can't restore back to the DB server right now to test it as it is a production server and down time granting is not immediately possible to test it ...
You do not have to restore to the same server or the same directory. You can keep your production system running and do a test restore somewhere else. Just make sure you specify --archive-mode=off (which prevents the WAL from being shipped from the restored system to your existing production repo)
[root@db1 data]# du -h
returns 537 G
This is not relevant, as pgbackrest only cares about the Postgres data directory (/data/edb/as16/data/)
149G /data/edb/as16/tablespace/ESS
This is where the rest of your backup size is coming from. Postgres and pgbackrest consider this part of the data directory.
You really should spin up a test Postgres cluster and get very familiar with how pgbackrest works, rather than continuing to flounder about on a production system and rely on mailing lists to answer a bunch of questions for you. While we can answer these questions, you will learn better from experimenting and trying things out yourself on a non-prod system.
