Would like an explanation of baynesian nash question and where the

 hello, i have attached a question with the solution/answer key. i am confused where the numbers like 1, -1, 0, in entrance payoffs come from in the key. i am also confused how they got the numbers in strategic form. i am mostly confused in the entrant’s payoffs section and would like clarification/explanation of where the numbers come from 

I need it in 5 hours maximum. Thank you