Reword ssl_conf_max_frag_len documentation for clarity
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 5593a52..9f44413 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -2106,12 +2106,23 @@
#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
/**
- * \brief Set the maximum fragment length to emit and/or negotiate
- * (Default: MBEDTLS_SSL_MAX_CONTENT_LEN, usually 2^14 bytes)
+ * \brief Set the maximum fragment length to emit and/or negotiate.
+ * (Typical: the smaller of #MBEDTLS_SSL_IN_CONTENT_LEN and
+ * #MBEDTLS_SSL_OUT_CONTENT_LEN, usually `2^14` bytes)
* (Server: set maximum fragment length to emit,
- * usually negotiated by the client during handshake
+ * usually negotiated by the client during handshake)
* (Client: set maximum fragment length to emit *and*
* negotiate with the server during handshake)
+ * (Default: #MBEDTLS_SSL_MAX_FRAG_LEN_NONE)
+ *
+ * \note On the client side, the maximum fragment length extension
+ * *will not* be used, unless the maximum fragment length has
+ * been set via this function to a value different than
+ * #MBEDTLS_SSL_MAX_FRAG_LEN_NONE.
+ *
+ * \note This sets the maximum length for a record's payload,
+ * excluding record overhead that will be added to it, see
+ * \c mbedtls_ssl_get_record_expansion().
*
* \param conf SSL configuration
* \param mfl_code Code for maximum fragment length (allowed values: