The Light Trigger Option will trigger the camera whenever the light values change suddenly.
The slider bar is used to set the sensitivity. Setting the sensitivity to 0 (zero) will trigger whenever light values change. Setting the slider midway will only trigger whenever light values change fairly quickly at once.
Some Android devices have only a "Light" and "Dark" light detector and will not detect the value of the brightness. If this is the case, the sensitivity should be set to 0.

"Shot Interval" will determined the interval between each shot taken while the Light values remain the same. Set this to zero to only take one picture right when the Light sensor is triggered.

Here is how the Settings screen looks after purchasing the Light Trigger option: