Hello
Note 12955 talks about the pegged requirements and it provides a good explanation about the system desing:
The respective current data on stocks, issues and receipts of the materials in question is evaluated in the pegged requirements display. There is no index that the system could use to determine which issue element (sales order, planning, reservation, dependent requirement, ...) is covered by a certain receipt element (purchase order, production order, purchase requisition, planned order, stock level ...). The current stock/requirements list for a material is determined in this case. The system then determines for each receipt element the issue elements that consume this receipt. In this case, the first x units of measure of the receipt on the time axis are consumed by the first x units of measure of the issues. Here, only the sequence and quantities of the receipts as well as the sequence and quantities of the issues are important. For the calculation it is unimportant whether the issue was made before or after the receipt or whether the issue and receipt quantities match each other.
BR
Caetano