diff --git a/AGENTS.md b/AGENTS.md
index 98e0b11..3b8e1cf 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -45,13 +45,44 @@ moby animation evaluator because doing so is what makes the result match.
 Do not "fix" something that looks like a bug until you have confirmed the
 original does the same thing. Fidelity beats correctness.
 
-### 3. Verify against the real disc, not against a guess.
+### 3. Never report a number without its bounds and its method.
+
+Any size, count or distribution quoted in a commit message, a doc or a test
+comes with two things attached: **which byte range it describes**, and **how
+it was measured**.
+
+This is not ceremony. Four separate numbers in one session looked
+load-bearing and turned out to be artifacts:
+
+- a format identified as VIF-packed, from a handful of recurring byte
+  patterns, where a control put it on the random baseline;
+- a body size computed over a span whose bounds were wrong, so the last
+  class absorbed most of the lump's tail;
+- a "6.2 MB of unidentified data" region that was texture data;
+- "3 unexplained blocks" that were an artifact of sampling too coarsely.
+
+All four shared one cause: measuring before bounding, and naming bytes before
+looking at them. None of them errored, which is why they survived long enough
+to be believed.
+
+Concretely:
+
+- Derive ranges from `gc_formats::regions::core_layout`, not by running from
+  one known offset to `core_data.len()`. Where a bound is unknown it is `None`,
+  not a guess.
+- Before calling a byte pattern a format, test it against a control. If a
+  statistic cannot tell your format apart from uniform random, it cannot tell
+  you anything.
+- A heuristic count is not an identification. Count distinct byte values, then
+  *look* at the blocks that stand out before naming them.
+
+### 4. Verify against the real disc, not against a guess.
 
 A parser is correct when it round-trips your own disc's bytes, checked by hash.
 Commit size-and-hash tables (never content) so a test can assert "this matches
 retail" rather than "this matches whatever was on my disk".
 
-### 4. Bound every read.
+### 5. Bound every read.
 
 Asset data is untrusted input from a 2003 disc format. Parsers return typed
 errors; they never panic and never read past the end of a buffer.