Yes, this calculation is correct but i want to know that if MRP was run on 19.05.2015 and purchase processing time is 0 days then release date should be 19.05.2015 and accordingly if we add 77 days to it delivery date should be 05.07.2015.
But here release date is 30.06.2015 and accordingly delivery date is calculated as 15.09.2015.