At Interactive Brokers I placed a limit combination order: SELL 6x SPXPM june 1500 BUY 6x SPXPM june 1510 for a limit price of 0.45 (credit) At setting up the combination order I have 2 choices: SMART and CBOE2 I choose CBOE2, there is only one place where these options are available so there is nothing smart. right ? Before I transmit the order, the Bid size is 138, Bid = 0.30, and the Ask size is 186, Ask = 0.70 After I placed the order the Ask size becomes my size of 6 and also my limit is now the new Ask. No fill yet. Can sombody explain this to me ?