I am using the Standard Value allocation method for the first time, sending costs from the Cost Source object to a manually created Lease Detail object.  The allocation is working as expected, matching the amounts in the target object based on the "Amount" column as I have setup.  And as expected the total allocation is not 100%, in this case only about $150k coming from Cost Source but $225k in the Lease Detail object.  My question is how can I calculate this amount and allocate it somewhere else (a manually created object to keep track of these differences) in order to have the financials tie out?

So in this example the ideal situation would be to have the following:

The idea being that we could then track the "Under/Over Allocation" object over time to see if the total is converging to $0 or trending and needs some attention.

I have found the following three posts which were insightful in general but I dont believe solved this situation Im having specifically.

Object Cost Allocation Fallout in Tabular Report 

Data Quality - Summary report 

Standard Value allocations 

Any help or guidance would be greatly appreciated.  Thanks in advance.

@Frank Lettiere, try this approach.

  
1. Add a line to the bottom of your lease detail table with the description "Over/Under"
  
2. Keep your 1st allocation line from cost source as is.
  
3. Add a 2nd allocation line from cost source to allocate the remainder to a line called "Over/Under"   
       
   1. From: Keep the same From filters with the exception of clicking the box for "send only remaining values"
       
   2. Allocate: Same models as first allocation line
       
   3. Using: Weighted value
       
   4. To: Same destination as first allocation line but introduce a filter so it only sends it to the "over/under" line
       
   5. Value: some numeric column you place in the table for that over/under line.  It needs to be a different numeric column than the 1st allocation line so that your standard value allocation still yields the desired result.
      

@Nancy Bugajski, thanks for the response.  This solution worked well.