Would like to ask if this is a correct behavior whne increasing qty if a component

Hi

Im using siebel 7.8 and was wondering if i issue an update order then on the order i customize the asset and increase the qty will it add a new line item with action code of add? or will it just update the existing component then update the qty and then action code to update?

ex.

Service 1

->Component 1
serial number=aaabb

Update Order

Service 1

->Component 1

Serial number=aaabb

customize to increase qty of componnet 1 to 2

what should have???