diff --git a/tests/test_lesson_insight_round_trip.py b/tests/test_lesson_insight_round_trip.py
index abc9ab7..8db7698 100644
--- a/tests/test_lesson_insight_round_trip.py
+++ b/tests/test_lesson_insight_round_trip.py
@@ -22,8 +22,13 @@ composer writes all of it after the marker, so paragraphs 2..n were ordinary
 lines that the filter had no reason to touch. They came back as "the
 insight", the full trigger was prepended again, and the stored lesson gained
 (n-1) paragraphs per update — silently, compounding, and in the half of the
-document that does the retrieving. On the corpus's worst real shape it grew
-the body by 520 characters over ten round trips.
+document that does the retrieving.
+
+Measured on the one real row this damaged (lesson #4207, a three-paragraph
+trigger): the body grew by exactly 607 characters per edit — the length of
+paragraphs 2 and 3 with their separators — taking it from 1291 characters to
+7361 over ten edits, at which point the trigger appears eleven times and the
+insight is 17% of the record.
 
 WHY A MARKER COULD NOT HAVE FIXED IT. There is no end-of-trigger marker in
 the body and adding one would not repair a row already written without it.