Unless I am mistaken, you had an initial equity issue. Its results equate to insufficient ONBP, but maybe for the sake of explanation, you could look at it this way.
You had 5500 in equitable securities, so with your marginal buying power equaling essentialy double your equity, you had 5400ish Buying Power. When you purchased more stocks with that money, you essentialy spent zero of your own money on the trade. ONBP works on the principle that at the end of the day, you can use roughly double "your" money. So essentialy if you had liquidated your prior securities and then repurchased them with the new ones. (Assuming same prices of course) You should have technicaly been ok with your holdings. (As long as none of them dropped below the minimum equity maintanence level) Hopefuly this answers your question, or hopefuly someone will correct me if I'm butchering the explanation.