User Interface serves the purpose

While visiting my parents' place, I found the following label on a light switch by a walk-in closet door.

'Off' is not the up-position.

It made me pause.  Wait, is the light switch flipped so that up position is on and down position is off?  I opened the door and checked.  No, it was not.  Light was turned off.  Mother must have labeled it wrong.

When I was stepping out in the morning, I saw another light switch label by the side entrance to the garage.  It also had an incorrect label except that it's even bigger.

'Off' is definitely not the up-position.
Label maker must have something else in mind.

Why would Mother put wrong labels on the light switches?  Doesn't she know that up is on, down is off?

Of course she does.  But that was not her point.  Her point was to remind everyone to check the light before we step out.  Closet light is easy to miss because it's controlled from outside the room.  Same is true for the side entrance light to the garage.  What she wanted was to grab everyone's attention so that we make the second glance at the light switch.

She put the labels where it's the most visible.  By doing that she accomplished her goal of making me look the second time.

My suggestion might have been to put 'Turn Light Off' instead of 'Off.'  But I could have been persuaded to abbreviate the label to 'Off.'  After all I'm the one who advocates the minimalistic design.  With a bit of up-front mental processing, I now know what to expect.  Consistent use of label helps me in this regard.

User Interface has to serve the purpose.  If it's intended to grab people's attention, it should grab the attention.