Total Amount of save data in NetWorker vs pre-compt data shown in Data Domain

Hi,

I'm looking to understand the relation between the amount of saved data shown in each job in NetWorker (At the top of each action: Backup) is shown Total Amount: XYZ GB

However, if i compare Total Amount of each NetWorker job and sum it up, the total is largely lower than the pre-compt shown in the Data Domain

NetWorker sums total = 131.5 TiB (NetWorker jobs runs every 24h)

Data Domain pre-compt = 271.5 TiB

Does anyone know why the numbers are so different ?

Thank you,

Chris