Foxbase Foxpro dBase code decipher tutor

I have an old program that was written in Foxbase plus / dBase - this was all DOS based - not pre Visual FoxPro. There are areas of the code where I need someone who has experience with this code to tell me exactly what it is doing. What calculations is it doing? What updates is it making to the data? You must be able to explain in very plain (for dummies) English what the old code does. This is essential. I am NOT looking for someone to write code or tell me how I should program my project. I just want you to look at the code and tell me what specific parts are doing. I am attaching a sample file you would be reviewing. I will tell you the basics of what this PRG file is doing and the areas where I need assistance with understanding.