fix various issues

- Naming
- format
- Reduce negative tolerance window

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index 2c7d946..33e8cc6 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -665,9 +665,7 @@
     return ( 0 );
 }
 
-/* Check if we have any PSK to offer, returns 0 if PSK is available.
- * Assign the psk and ticket if pointers are present.
- */
+/* Check if we have any PSK to offer, returns 0 if a PSK is available. */
 MBEDTLS_CHECK_RETURN_CRITICAL
 static int ssl_tls13_get_psk_to_offer(
         const mbedtls_ssl_context *ssl,
@@ -810,12 +808,10 @@
     {
 #if defined(MBEDTLS_HAVE_TIME)
         mbedtls_time_t now = mbedtls_time( NULL );
-        uint64_t age_in_ms =
-                     ( now - ssl->session_negotiate->ticket_received ) * 1000;
 
         obfuscated_ticket_age =
-            (uint32_t)( ( age_in_ms + ssl->session_negotiate->ticket_age_add )
-                        & ( ( 1LL << 32 ) - 1 ) );
+            ( (uint32_t)( now - ssl->session_negotiate->ticket_received ) * 1000 )
+              + ssl->session_negotiate->ticket_age_add;
 #endif
     }
     else