What was the code on your DM card? Voluntary standby is usually BP5B (if you misconnect it's BP5A). The only nonrev UA travelers that should rank above these are company officers (BP1A), priority flight crew (BP1B), UA business or emergency, outbound (BP3). Nonrev positive space is BP5C, and space available is BP7. The full list of these codes was given here some time ago.