Hi @girish,
You can update the quantity of the purchase order line when it is partially received and if you are handling the multi-site order then you can propagate this changes to all the pegged order in the supply change automatically ( if you have properly defined the message defaults for supplier & customer) or manually as well.
Meanwhile, you can also receive the over deliveries against the purchase order, system will prompt with the information message and this depends on the over delivery setting you defined on site, purchase group & purchase part.
Hope this helps!!
Regards,
Mithun K V