I just had it on regular photo and it did something with a kind of timer on its own. All I did was press the button to take the picture. I just looked it up, and it looks like this explanation is how it happened. Sorry if this is confusing :(

“The Night mode (moon) icon appears at the top of the Camera app when you shoot in low light. If the Night mode icon is white, tap it to activate Night mode. If the icon is yellow, Night mode is already switched on.”