This means that your parts have arrived from the supplier and the unit is being re-assembled, the technicians will assemble the unit and test it,. The unit may however not pass this initial test process and may potentially have to be re-assessed based on the test results, A unit could have multiple things wrong with it, ordering a part and fitting it may not necessarily mean it's fixed, there could be a secondary fault which due to the first fault could not be diagnosed,

 

For example, if the unit’s screen is broken, it may have had a HDD (Hard Drive) failure which could not be diagnoses due to the screen failure.