What is this strange circle with the number 5 in full screen mode on android? And how to remove it?

Question

Android

A strange circle appears on pixel 6 in full screen mode, taps do nothing on it, it can also be hidden in any part of the screen, does anyone know what it is and how to remove it?

Answer 1

As it turned out, this is an FPS indicator that is turned on in the game mode, it is also turned off in it, there is a bug that it may not disappear, then only restarting the phone will save