diff --git a/docs/requirements.md b/docs/requirements.md
index 21e44c95f..8a1501efb 100644
--- a/docs/requirements.md
+++ b/docs/requirements.md
@@ -109,6 +109,8 @@ change history be made public. Rather, some organization must attest to the fact
 that these requirements are met, and it is up to the consumer whether this
 attestation is sufficient.
 
+"○" = RECOMMENDED.
+
 <td>○<td>✓<td>✓<td>✓
 <tr id="verified-history">
 <td>Verified history