Need your help with forecasted quantity

I am having the following.

Product: Table Orderpoint: Min:50 BOM Table Leg x 4 Table Top x 1 Table Screws x 16 Procurement Method: Make to Stock supply Method: Manufacturing

Table Leg: Order Point:20 Supplier ABC Company Minimum Order:0 which is default Procurement Method: make to Stock Supply Method: Buy

Table Leg: Order Point: 80 Supplier DEF Company Minimum Order:1 Procurement Method: make to Stock Supply Method: Buy

Table Screw Order Point: 320 Supplier GHI Company Minimum order: 0 which is default Procurement Method: make to Stock Supply Method: Buy

A Customer ask for quotation of 15 Tables and Order is confirmed. When I verify Warehouse: Delivery order: Qty 15 Waiting Availability

Draft PO Generated: Total Unit for DRAFT PO as follows

Table Top: 85 (50 Order Point for Table, 20 Order point for Table Top, 15 Customer Order)

Similarly for Table leg has Draft PO:340 (85x4 legs per table)

Table Screw has Draft PO:1360 (85 x 16 screws per table)

When I confirm Draft PO and Receive products Quantity on hand match with Draft PO. But there is a Forecasted Quantity of

Table: 50 Table Top: 20 Table Leg: 80 Table Screw: 320

My question is Since the initial PO contains all quantity as per order level set in Bill of Material and Product. Why system still shows Forecasted quantity?

Thank you