diff --git a/applications/condition/load_report.py b/applications/condition/load_report.py
index bf0f2fc73..21bbf7553 100644
--- a/applications/condition/load_report.py
+++ b/applications/condition/load_report.py
@@ -7,7 +7,15 @@ from domain.condition.records.calico.calico_property import CalicoProperty
 @dataclass(frozen=True)
 class LoadReport:
     """The reconciliation a Calico load emits so nothing vanishes silently
-    (ADR-0064): how many observations were loaded versus dropped, and why."""
+    (ADR-0064): how many observations were loaded versus dropped, and why.
+
+    ``loaded``, ``unmatched_to_portfolio`` and ``blank_placeholder`` account for
+    the Calico rows. ``null_uprn`` is a portfolio-wide data-quality canary — the
+    count of properties in the portfolio whose UPRN is null (expected: zero) —
+    *not* a per-row drop reason, so it does not partition with the others: a
+    Calico reference pointing at a null-UPRN property is reported both here and
+    under ``unmatched_to_portfolio``.
+    """
 
     loaded: int
     unmatched_to_portfolio: int