Need Amibroker Afl: calculate total number of Black,White candles for 30min timestamp

Example: I have 1000 stocks in amibroker , my time stamp is 30 mins


Expected:
1. need the black and white candle count of every 30 minutes from this 1000 stocks.

Need Amibroker Afl: calculate total number of Black,White candles for 30min timestamp