Why there is 30000 rows is sample

Hi!

vacuumdb output:

vacuumdb: vacuuming database "mydb"
INFO:  analyzing "public.mytable"
INFO:  "mytable": scanned 2709 of 2709 pages, containing 10834 live rows and 0 dead rows; 10834 rows in sample, 10834
estimated
 
total rows

For tables with more than 30000 rows, it shows that there are 30000 rows in sample.

postgresql.conf does not set  default_statistics_target value.
It contains

#default_statistics_target = 100    # range 1-10000

So I expect that there should be 100 rows is sample.
Why Postgres uses 30000 or number of rows in table for smaller tables ?

Is 30000 some magical value, how to control it.

Using Postgres 12 in Debian.

Andrus.