This excerpt taken from the C DEF 14A filed Jun 18, 2009.
Q: What options do I have with respect to the proposals?
A: If you are a holder of Public Preferred Depositary Shares or Trust Preferred Securities and you wish to tender your securities in the Exchange Offers, then you must follow the procedures contained in the Letter of Transmittal to give your Proxy Instructions to approve the Common Stock Amendments (which is equivalent to a vote for each Common Stock Amendment).
If you hold shares of common stock that were not issued in the Exchange Offers, with respect to such shares of common stock, you may give a proxy authorizing the individuals designated by Citigroup on the enclosed proxy card to execute a written consent to consent to (which is equivalent to a vote for the proposal), to withhold consent (which is equivalent to a vote against the proposal), or to abstain on each proposal. If you give a proxy to abstain on any stockholder proposal, the abstention will have the same effect as a vote against that proposal.