Only on all possible profit figures

I do not for one bit understand how you generated those possible profits from the topic : risk and uncertainty: I have been enjoying your lectures so far and good but this is the only place I have had to replay the video often and often.
Maximin, maximax and maximax regret are all well understood and without the major profit figures i can not do others.

Major problem ,

I understand from the choices of 300unit and the normal demand units of uncertianty figures and the resulting profits.
But, the next, according to question is 500, 700 and 800units as choices
If i choose 500 , what is the next normal uncertain units i am suppose to choose to arrive at the profit you got? All start from 400, 500, 700 and 900
You choose 300 and use 400 to get the profits of 2900
If i choose 500units what will be the normal demand to choose from among 400,500,700 and 900?
And 700 and thereafter 800.
I think this will help tackle other questions in the exams.