diff --git a/goodwe_controller/test_mqtt.py b/goodwe_controller/test_mqtt.py
index e1b7183..5d44b92 100644
--- a/goodwe_controller/test_mqtt.py
+++ b/goodwe_controller/test_mqtt.py
@@ -272,11 +272,21 @@ print("\n1. the recorded baseline, and a roster of one")
 # entity on a live install.
 m, c, a = report("roster of one (`inverters:` empty, i.e. every install today)",
                  announce(units=roster_names({})))
-check("⭐ AT THE SHIPPED ROSTER OF ONE EVERY ONE OF release/1.0's NINE "
-      "MESSAGES IS STILL BYTE-IDENTICAL AND STILL FIRST: same topics, same "
+# ⚠️ THE HEADLINE SAYS EIGHT, NOT NINE, AND THE SLICE UNDER IT IS WHY.
+# release/1.0 announces NINE messages; the ninth is `goodwe_ctl/availability`,
+# which `_announce()` publishes LAST and which TEL-10 therefore MOVES - it is
+# byte-identical but no longer at index 8. So what is asserted here is the eight
+# entity CONFIGS, `[:len(BASELINE) - 1] == BASELINE[:-1]`, and the word "nine"
+# above it named an assertion this file does not make. The ninth is not
+# unguarded: the `== SITE_NOW` on the next check pins it byte-for-byte in its
+# new last position. Two sentences, two checks.
+check("⭐ AT THE SHIPPED ROSTER OF ONE EVERY ONE OF release/1.0's EIGHT ENTITY "
+      "CONFIGS IS STILL BYTE-IDENTICAL AND STILL FIRST: same topics, same "
       "unique_ids, same payload bytes, same retain flags, in the same order - "
       "no second device, no renamed entity, nothing re-ordered. TEL-10 adds "
-      "rows AFTER them; it may not move one of them",
+      "rows AFTER them; it may not move one of them. (release/1.0's NINTH "
+      "message, `availability`, is byte-identical too and deliberately moves "
+      "to LAST; the `== SITE_NOW` below is what pins it)",
       announce(units=roster_names({}))[:len(BASELINE) - 1] == BASELINE[:-1])
 
 # ⚠️ AND THE ADDITION IS ITS OWN CLAIM, WITH A COUNT. "Nothing moved" and
@@ -333,8 +343,10 @@ check("⭐ AC 1: AT A ROSTER OF TWO, EVERY ONE OF A's NINE MESSAGES IS STILL "
       (m, c) == ([], []))
 check("...and the eight additions are all B's and A's own per-unit rows, and "
       "all of them are NEW topics", len(a) == 8)
-check("...and A's nine messages are still the FIRST nine, in the same order, "
-      "so a broker replaying retained messages sees them unchanged",
+check("...and A's eight entity configs are still the FIRST eight, in the same "
+      "order, so a broker replaying retained messages sees them unchanged "
+      "(the ninth, `availability`, is byte-identical and last - the check "
+      "above is the one that covers it, as a diff rather than a prefix)",
       TWO[:len(BASELINE) - 1] == BASELINE[:-1])
 
 # ⚠️ THE SITE SET IS `SITE_NOW`, NOT `BASELINE`. Read from `BASELINE` it would
diff --git a/goodwe_controller/test_telemetry.py b/goodwe_controller/test_telemetry.py
index a41d52c..b93d9ce 100644
--- a/goodwe_controller/test_telemetry.py
+++ b/goodwe_controller/test_telemetry.py
@@ -32,11 +32,20 @@ the revert (MUTATION.md's reporting rules, and habit 18's unique backup path).
   M4  delete `self.loop_reason = "not-running"`        -45 B    1   this file
   M5  delete the not-running branch's two zeroes       -67 B    1   this file
   M6  `"loop_i": round(self.target, 1)`                 -2 B    4   this file
-  M7  the `loop_i` row deleted from `SENSORS`          -96 B  8+1   test_mqtt
+  M7  the `loop_i` row deleted from `SENSORS`          -96 B 10+1   test_mqtt
                                                                       + this file
   M8  `loop_i` announced PER INVERTER                  +89 B    8   test_mqtt
   M9  `loop_i` announced BEFORE release/1.0's nine      +0 B    7   test_mqtt
 
+⚠️ A RED COUNT IS A PROPERTY OF THE SUITE AS MUCH AS OF THE MUTATION, SO EVERY
+ONE ABOVE NAMES A TREE - this one, at this commit. A later card that adds a
+check, re-baselines one or deletes one moves the number with the mutation
+untouched. Re-measure rather than inherit: `tools/mutation_run.sh` on a `cp -a`
+of the tree, one file at a time, and say which tree. M7's count was written as
+8 and is 10 on a re-run, on both trees - the direction was right and the count
+was decoration, which is the half of MUTATION.md's reporting rule 3 that is
+easiest to let rot.
+
 ⚠️ M9 IS ZERO BYTES AND CHANGES NO PAYLOAD. Every id, name, unit and topic is
 identical; only the ORDER of the retained messages moves. No fingerprint and no
 byte delta can see it, which is why part 1 asserts the announcement as an