how to handle residual quantities of ingredients in a silo/

Hello,

We have a 1000 lb tank to store ingredient powders (i.e. flour).   The silo holds multiple lots.  When the silo is empty, there is still some residue from the previous lots.  This means that, unless we thoroughly clean the silo at regular intervals, the batch will consist of a very small amount of the oldest lot.

If I pull ~100 lbs of this ingredient for each batch equally, eventually I will run out of Lot 1, but in reality, there is always a very small amount of Lot 1 remaining.  If I always pull 100 lbs, Oracle will think there is zero onhand after the 10th batch.  However, this isn't true because of the residue.  We want to make sure we include Lot 1 in the lot genealogy of the batch in the event of an ingredient recall by the vendor but we don't want Lot 1 to remain in each batch forever.  How do most