Why are the OHLC values on daily and hourly charts different?
The minute and hourly candles are formed by the live data we receive from the exchange. This data is not tick by tick data meaning it doesn’t include all the transactions that took place in that time interval.
But, the OHLC (open, high, low, close) values are updated once again after the trading day ends, with data from the ‘bhavcopy’ provided by the exchange. The exchange OHLC for the day on bhavcopy will be 100% accurate as it will be created using all the ticks that happened on the exchange.
Unfortunately, the exchange doesn’t share minute/hourly OHLC for the day in the bhavcopy, so the minute/hourly charts will be formed using the ticks that we have received in our feed from the exchange and daily charts using the OHLC that exchange has sent on ‘bhavcopy’ - hence the mismatch.
For more information read this post on TradingQ&A.