How is the default user given sudo access without being listed in sudoers?

I have a question about command sudo.

Basically, you know, sudo allows any permitted users who enrolled in the /etc/sudoers to perform some commands specified in it.

At this point, I wonder how my default user account can use sudo.

The following is content of my /etc/sudoers file.

# This file MUST be edited with the 'visudo' command as root.
#
# Please consider adding local content in /etc/sudoers.d/ instead of
# directly modifying this file.
#
# See the man page for details on how to write a sudoers file.
#
Defaults        env_reset
Defaults        mail_badpass
Defaults        secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

# Host alias specification

# User alias specification

# Cmnd alias specification

# User privilege specification
root    ALL=(ALL:ALL) ALL

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL

# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL) ALL

# See sudoers(5) for more information on "#include" directives:

#includedir /etc/sudoers.d

As you see, my account - jwl - is not registered in that file. But I can use sudo command without any problems. How can it be possible? Is there any mechanism I don't know? If so, let me know it.

Thank you for reading.