I am starting to learn how to use Airflow for pipelines.
I have the simplest DAG in

from __future__ import annotations

import textwrap
from datetime import datetime, timedelta

# The DAG object; we'll need this to instantiate a DAG
from airflow.models.dag import DAG
# Operators; we need this to operate!
from airflow.operators.bash import BashOperator

with DAG(
    dag_id="simplest_tutorial",
    # [START default_args]
    # These args will get passed on to each operator
    # You can override them on a per-task basis during operator initialization
    default_args={
        "depends_on_past": False,
        "email": ["[email protected]"],
        "email_on_failure": False,
        "email_on_retry": False,
        "retries": 1,
        "retry_delay": timedelta(minutes=5),
    },
    description="An even simpler tutorial DAG",
    schedule=timedelta(days=1),
    start_date=datetime(2021, 1, 1),
    catchup=False,
    tags=["example"],
) as dag:

    t1 = BashOperator(
        task_id="print_date",
        bash_command="date",
    )

    t2 = BashOperator(
        task_id="sleep",
        depends_on_past=False,
        bash_command="sleep 5",
        retries=3,
    )

t1 >> t2

When I run this DAG I get this in Airflow

Airflow DAG screen

so it seems the DAG has been ran twice!.

Also if I click on the green bars to the left I can see that

one run was not externally triggered and the other one was.
The audit log is also difficult to understand

Audit log

Why is this DAG being run twice?