Lot size in material master
Please advise my below understanding is correct. If we select EX in lot size field in mrp views, mrp will generate the pr of qty equivalent of sales order qty. if we select FX, it will generate the pr of qty equal to fixed lot qty mentioned in mrp views. While calculating the above qty it will deduct the existing stock of that material and for remaining qty, it will generate pr (purchase requisition).
If sales order is 100, and the shortage is 1, then that implies that you have 99 in stock available for this order. In this case, if the lot size is EX, then the proposal will be for 1.
You really would be better off experimenting in a sandbox system. 20 minutes of work in the sandbox could answer dozens of these questions, and the resulting answers are instantaneous.