In games and animations, zz is often used to indicate that someone is asleep, and then the symbol zz becomes the representative symbol of falling asleep. The appearance of this in Huawei's sleep check also represents sleep.
The sleep test is opened as follows, 1. In Huawei Health app, go to the watch details page and click Sleep Test. 2. Click on the scientific sleep option. 3. Just turn on the switch button on the right side of the scientific sleep.