The integration time settings defines how long the Ambient Light Sensor collects light for a single measurement.
Continuous Mode
This mode allow that the light sensor continuosly measure the light intensity, once a measurement is finished and the result stored, the next one ins immediately started.
High Brightness
This mode, only 1/8 of the photo diode current is used as input for the Analog to Dialog Converter (ADC). This setting is used in high-brightness situations to avoid saturation/clipping effects of the ADC.