diff --git a/book/source/06-certifications.md b/book/source/06-certifications.md
index 11bb9ea..b8b9ae4 100644
--- a/book/source/06-certifications.md
+++ b/book/source/06-certifications.md
@@ -40,15 +40,15 @@ flowchart LR
     certification --> uidcert & uidrev & dksig & krev
     subgraph Siganture Types and Targets
         standalone[0x02: Standalone]
-        subgraph Signature Packets
+        subgraph Signature Packet
             confsig[0x50: Third-Party Confirmation]
             timestamp[0x40: Timestamp]
         end
-        subgraph Data Packets
+        subgraph Data
             binary[0x00: Binary Data]
             text[0x01: Canonical Text]
         end
-        subgraph User ID / User Attribute Packets
+        subgraph Primary Key + User ID / Attr. Packet
             uidcert[
                 0x10: Generic Certification
                 0x11: Persona Certification
@@ -61,7 +61,7 @@ flowchart LR
             dksig[0x1F: Direct-Key Signature]
             krev[0x20: Key Revocation]
         end
-        subgraph Subkeys
+        subgraph Primary + Subkey
             skbind[
                 0x18: Subkey Binding
                 0x19: Primary Key Binding