i cannot set the ramp times as there is no duration column in the illumination table.
What do you need a duration time for? You set points and the ramp is between this two points. Example:

You set 9:00-5% and 11:00-30% -> this results in an ramp from 9:00 to 11:00 increasing the illumination.
If you would set both points to 5% you would get a stable light value aka two hours of your duration.

There is nothing missed, it´s a different logic to what you expect.