Add clarification on 2.x branch choice

Signed-off-by: Werner Lewis <werner.lewis@arm.com>
diff --git a/docs/3.0-migration-guide.md b/docs/3.0-migration-guide.md
index 8474069..14c8aa8 100644
--- a/docs/3.0-migration-guide.md
+++ b/docs/3.0-migration-guide.md
@@ -25,7 +25,8 @@
 migration path is not provided in prior documentation, changes made and the
 upgrade steps required will be explained in this guide.
 
-To generate the documentation, checkout the `mbedtls-2.28` branch and follow
+It's best to use the latest version of Mbed TLS 2.x for this purpose, which is the 2.28 LTS release.
+So to generate the documentation, checkout the `mbedtls-2.28` branch and follow
 the instructions in the [Documentation section of the README](https://github.com/Mbed-TLS/mbedtls/blob/development/README.md#documentation).
 Then browse `apidoc/deprecated.html` for guidance on upgrading deprecated code.