Meaning of "pg_control version number:"

Hi,
I supposed "pg_control version number:" is related to pg version, but fresh
pg 15 instance pg_controldata shows 1300:

$ initdb -V
initdb (PostgreSQL) 15.1
$ initdb
The files belonging to this database system will be owned by user
"postgres".
This user must also own the server process.

The database cluster will be initialized with locale "en_US.UTF-8".
The default database encoding has accordingly been set to "UTF8".
The default text search configuration will be set to "english".

Data page checksums are disabled.

fixing permissions on existing directory /pgdata/pgsql/15/data ... ok
creating subdirectories ... ok
selecting dynamic shared memory implementation ... posix
selecting default max_connections ... 100
selecting default shared_buffers ... 128MB
selecting default time zone ... Europe/Tallinn
creating configuration files ... ok
running bootstrap script ... ok
performing post-bootstrap initialization ... ok
syncing data to disk ... ok

initdb: warning: enabling "trust" authentication for local connections
initdb: hint: You can change this by editing pg_hba.conf or using the
option -A, or --auth-local and --auth-host, the next time you run initdb.

Success. You can now start the database server using:

pg_ctl -D /pgdata/pgsql/15/data -l logfile start

$ pg_controldata -V
pg_controldata (PostgreSQL) 15.1
$ pg_controldata /pgdata/pgsql/15/data | grep "pg_control version number:"
pg_control version number: 1300

br
Kaido