Unidentified Amounts with Backflushed production order.

I am performing testing on a client’s BOMs whereby materials and labor are both backflushed. The BOMs are quite simple in nature with one or two work centers. At this time we have a zero rate applied to the work center since the client has not determined the appropriate value. When production is completed and the move step is initiated, I see the materials go into WIP at the proper cost. The labor cost does not generate entry since the work center rate is 0. When I check the move out of WIP and into inventory, there is an unknown component to the entry whereby COGs and Inventory are impacted but there is not reflected in the cost of the item, nor should it be. I cannot figure out what is driving this entry.  See screenshots for example. Any idea why the highlighted portion of the entry in the last screenshot is happening?  Client uses Average Cost valuation method for inventory. I tried the Cost Roll process to see if this would fix the issue but it has not.