diff --git a/tailbone/views/purchasing/receiving.py b/tailbone/views/purchasing/receiving.py
index 9316c2a9..711daac1 100644
--- a/tailbone/views/purchasing/receiving.py
+++ b/tailbone/views/purchasing/receiving.py
@@ -702,22 +702,17 @@ class ReceivingBatchView(PurchasingBatchView):
                     cases = update_form.validated['cases']
                     units = update_form.validated['units']
 
-                    # try to be smart about how we update cases and units for row
-                    existing = getattr(self.handler, 'get_units_{}'.format(mode))(row)
-                    proposed = existing + self.handler.get_units(cases, units, row.case_quantity)
-                    new_cases, new_units = self.handler.calc_best_fit(proposed, row.case_quantity)
-
-                    old_cases = getattr(row, 'cases_{}'.format(mode))
-                    if new_cases and old_cases != new_cases:
-                        setattr(row, 'cases_{}'.format(mode), new_cases)
-                    elif old_cases and not new_cases:
-                        setattr(row, 'cases_{}'.format(mode), None)
-
-                    old_units = getattr(row, 'units_{}'.format(mode))
-                    if new_units and old_units != new_units:
-                        setattr(row, 'units_{}'.format(mode), new_units)
-                    elif old_units and not new_units:
-                        setattr(row, 'units_{}'.format(mode), None)
+                    # add values as-is to existing case/unit amounts.  note
+                    # that this can sometimes give us negative values!  e.g. if
+                    # user scans 1 CS and then subtracts 2 EA, then we would
+                    # have 1 / -2 for our counts.  but we consider that to be
+                    # expected, and other logic must allow for the possibility
+                    if cases:
+                        setattr(row, 'cases_{}'.format(mode),
+                                (getattr(row, 'cases_{}'.format(mode)) or 0) + cases)
+                    if units:
+                        setattr(row, 'units_{}'.format(mode),
+                                (getattr(row, 'units_{}'.format(mode)) or 0) + units)
 
                     # if mode in ('damaged', 'expired', 'mispick'):
                     if mode in ('damaged', 'expired'):