It’s just a number. Minutes are arbitrary. 12 is arbitrary.
Sit. Sit comfortably. Sit still. Don’t get fancy.
Set a timer for 12 minutes.
Open your eyes.
Fail to notice your breath. Continue to fail to notice your breath.
Notice everything around you. Avoid focusing on anything.
Look straight ahead. Blink. Fail to notice that you blink. Keep looking straight ahead.
Keeping noticing and allow noticing to flow.
When a thought arises, let it pass. Hold quiet.
Time’s up. Turn off the timer. Get up. Move about.
Do this once a day, many days a week.