My account shows a ton of Margin (4 times my equity for daytrading)...but that is automatically reflected...(because they haven't figured out how to segregate the "concentration rule" exclusion). So I called up before I used it because I got caught in it once before. I would suggest doing the same before you use it.
ThinkorSwim, which is now part of TD Ameritrade (unfortunately)has the rule I articulated. Other brokers have similar rules but not exactly the same.
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