In reorder point planning, the system compares the available stock with the reorder point to determine the net requirements. If the available stock falls below the reorder point, the system triggers a procurement proposal for the material. The quantity of the procurement proposal depends on the lot size procedure that is defined in the material master. The lot size procedure determines how the system calculates the order quantity based on factors such as demand, costs, and storage space. There are different types of lot size procedures, such as static, periodic, or optimum lot size. Reference: [Production Planning with SAP S/4HANA], page 156; [SAP Help Portal: Lot Size Calculation].