Hi Mohamed,
I dont know of a specific way to do this in Xtraction off hand. The challenge is that in our object layer, we have the "pdm_downtime" function that can be called to calculate that - however, Xtraction does not report against our object layer, but rather reports directly against the MDB via the Xtraction data model. I dont believe there is a function in the Xtraction data model to do that calculation, so most likely the data would need to be pulled into Xtraction and then a calculation applied to it. There might be some folks out here in the community that have done this and can share their info with you.
Regards,
Jon I.