Large backup size of pg_dump

Hello,

I am using PostgreSQL 18.4 x64 on Windows Server 2022. There is a very
small single database in the cluster.

There are hourly pg_dump backups scheduled and database backup size is
around 10GB.

command line is like below
pg_dump.exe -p 5432 -U dbuser --exclude-table=app -F p -b -c -f "hourly.bak"

When I check the cluster directory size it is 4.1 GB.

Database has one BLOB saved in a single record and it is 16MB in size and
that is in the "app" table which is excluded from the backup file.

I didn't understand about 2.5 times bigger backup sizes than the total
cluster size. I do not know what to check either. Is there a way for me to
make the hourly backup size smaller?

Thanks & Regards,
Ertan