The Timed Release mode is the perfect solution if you want to control the shutter with great precision. This mode has a single parameter:
Exposure: This parameter controls the exposure in hours, minutes, seconds and milliseconds. In order to change the parameter, touch the exposure value and a numeric keypad will appear. You can type in the desired exposure value and then touch anywhere outside of the circle. The new exposure value will be shown in the circle. Touch the notch on top of the circle and then pull the curtain down. You can start the exposure by touching the orange button again.