As brokers, we are required to maintain segment wise balance for all accounts. Accordingly if you transfer any money to your trading account, the credit would be given to NSE-EQ segment. However these funds would be available for trading in any segment.
For eg: If you have transferred Rs.100 to your trading account, credit of these would be given to NSE Eq segment. However you can use these funds to trade in Equity/F&O/CDS Segment provided you have the segment enabled. If you utilize these funds for trading in F&O and make a loss of Rs.30 then your NSE Equity Balance would continue to show Rs.100 credit while your F&O segment would show a balance of minus 30 thereby making your balance across all segments as Rs.70 (100cr in EQ - 30dr in F&O).
You will have to view your balance across all segments to know the balance you are holding in your account. Bracket would indicate that the balance is a negative.