That icon is telling you how long the shutter will stay open while taking the photo. Adding more light to the subject will allow the phone’s camera to take a faster photo.

You can use switch the up carrot center top to down carrot and turn it off manually.

Night mode. If you have a tripod you can set it to 30 seconds. It is really amazing what it can do.

Sheep

That’s night mode and you can tap on the icon to disable it.