I want to sell a part of my holdings of one stock, but I am not able to do so, as I am getting the error that I must keep $500 worth of holdings of that stock in my account.
So does that mean I can sell a part of my holdings provided I keep $500 worth of those holdings in my account ? So if I have bough $750 worth of stock, so I can only sell $250 worth of it ?

And in case I can't sell a part of the stock without keeping $500 worth of those holdings, so in that case I'll just have to sell all of it.
Considering the previous example - what if I want to sell $350 instead of $250, I can't do that, so can I still sell the entire holding ?