The screen of Jiaming Watch lit up when it was in fun run, probably because the flip screen setting was turned on. This is a common function. When the user's wrist flips, the watch will automatically light up the screen for the user to check the time or other information. If you don't want the screen to light up when fun run is running, you can turn off the wrist flip function in the settings of Jiaming Watch.
The above information is for reference only. It is recommended to consult professional and technical personnel or check the instructions.