Should i try counting stairs at school?

no.

Why not it actually a good game, i guess

I think I first heard it as one of the famous Japanese highschool horror myth.
Irl its mostly how our brain function in different circumstances, including cultures, ethics, temporary body statistics, etc. For ex. When you walk up and start counting, you easily count the ground your on as 1, making total of 13 steps. But when you go down, you easily forget to count the plane that you are on, making it 12 steps in total.
If you do go to another dimension or world, the trend in this era is not the fantastical one anymore, but rather “Am I hallucinating?” “Simulacra/simulacrum, green/blue pill or red pill?” “Is this just my mental effecting my vision and my body is being hospitalized or in the psychiatric?” etc.
The classic post modern “man vs reality”