Ending Available Calculation

Hi Team,

I am trying to understand the calculation for End available. I read the E guide for this but not under stand. In the attached screen shot could you please explain me how the calculation is done for End Available in 2, 3 ,4, 5 and 6th period.

Assume that the order policy code equals lot for lot, safety stock equals 20,On Hand Quantity= 80, time fence rule for planning equals C, and lead time equals 1. The planning fence is between periods 4 and 5.

Thanks in advance.