a few more doc changes to gcm tag info
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index f009bb7..6e3c102 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -357,9 +357,10 @@
Cryptography will emit a 128-bit tag when finalizing encryption.
You can shorten a tag by truncating it to the desired length, but this
is **not recommended** as it lowers the security margins of the
- authentication (`NIST SP-800-38D`_ recommends 96-bit or greater).
+ authentication (`NIST SP-800-38D`_ recommends 96-bits or greater).
If you must shorten the tag the minimum allowed length is 4 bytes
- (32 bit).
+ (32-bits). Applications **must** verify the tag is the expected length
+ to guarantee the expected security margin.
:param bytes tag: The tag bytes to verify during decryption. When encrypting
this must be None.